Adding and Subtracting from Torah/2

Adding and Detracting from Torah

Exegetical Approaches

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Overview

Commentators debate the scope of the prohibition against adding or detracting from Torah, and question how it bears on the ability to enact Rabbinic decrees. The various approaches raise important questions about both the extent of Rabbinic authority and the eternal nature of Torah and its laws.  In several cases, commentators' stances might be influenced by polemical concerns.

R"Y Kara and Chizkuni limit the prohibition to the realm of religious worship, seeing in it a warning against adopting Canaanite cultic practices. This narrow reading easily explains why Rabbinic safeguards are not considered a violation. The Kuzari limits the law in another way, claiming that it is aimed only at the masses. Leaders such as sages, prophets, or priests, are not included and are, thus, free to enact laws as they deem necessary.

The Sifre narrows the scope of the prohibition in yet a third manner, asserting that it applies only to changing the form of an existing law. As such, Rabbinic enacting of new laws is not problematic.  Ramban, in contrast, does not limit the law and suggests that it relates to adjusting both existing commands and creating new ones. Rabbinic safeguards are exceptional only because the Torah itself commands that one put such fences in place.

Limited to Specific Mitzvot

The prohibition of "not adding or detracting" is limited in scope and is relevant only in the realm of religious worship.

Sources:R. Yosef KaraDevarim 13:1About R. Yosef Kara, ChizkuniDevarim 4:2Devarim 13:1About R. Chizkiyah b. Manoach #2,

The exact prohibition – Both these sources agree that the prohibition forbids adopting Canaanite practices into one's worship of Hashem, but they offer two variations of the specific actions which are being forbidden:

• Idolatry – Chizkuni on Devarim 2 asserts that the prohibitions pertain to idolatry, warning both against worshiping additional gods and detracting from the worship of Hashem.¹
• Sacrifices – R"Y Kara (and Chizkuni on Devarim 13),² instead, suggest that the prohibitions relate to the sacrificial service. The verses mandate that one bring sacrifices only from animals or birds, rather than from humans or from nothing at all.  One should not "add" and sacrifice also children, or "detract" and spare the animals.

Context – The two readings are supported by the context of the prohibition:

• Idolatry – Chizkuni notes that the command appears twice in Torah, both times in the context of idolatry.³⁴
• Sacrifices – R"Y Kara looks to the broader context of Devarim 13:1, to Chapter 12 as a whole,⁵ which discusses centralization of worship and proper sacrifices.⁶

Purpose and necessity of the law – Considering that warnings against both idolatry in general and child sacrifice in particular exist elsewhere, one might question what is added by this prohibition.  These sources might agree that there is no new content being introduced and suggest that the verses simply provide yet another warning due to the severity of the crime.

Biblical cases – Given the limited parameters of the law,  none of the Biblical characters who enacted their own decrees,⁷ temporarily suspended⁸ or adjusted existing laws,⁹ were in violation of "לֹא תֹסֵף".

What about rabbinic laws? As the prohibition of adding or detracting is limited to the realm of cultic practice, it does not forbid adding to other existing laws or even instituting an entirely new one. Chizkuni, thus, emphasizes that Hashem never prohibited adding safeguards to ensure proper observance of His laws. Though Chizkuni does not say so, according to his reading, it would appear that even those without Rabbinic authority should be allowed to do so.

Other potential cases of "לֹא תֹסֵף" – According to this approach, observing a mitzvah outside of its mandated time,¹⁰ performing it multiple times, or voluntarily taking on a mitzvah from which one is exempt would not be a violation of "לֹא תֹסֵף".

Polemics – Chizkuni is explicitly polemical in his comments, opening by saying, "תשובה למיני ישראל שפקרו על התלמוד".  He might be referring to the Karaites who reject the Oral law and Rabbinic decrees, pointing to the prohibition of "do not add" as proof that these are invalid.¹¹  In limiting the scope of the law, Chizkuni renders their arguments baseless.

Relationship between "לֹא תֹסֵף" and "לֹא תִגְרַע" – According to this approach, the two statements constitute two distinct prohibitions, each the flip side of the other.

Relationship between Devarim 4 and 13 – This approach could say¹² that each verse prohibits additions to a distinct mitzvahץ One warns against worshiping additional gods and the other against adding to the list of permitted sacrificial items.

Applicable Only to the Masses

The directive is aimed only at the masses.  Leaders such as prophets or judges are given the right to add to or detract from the Torah's commandments.

Sources:Kuzari3:39-41About R. Yehuda HaLevi, Hoil MosheVayikra 16:8Vayikra 19:19Vayikra 24:19Bemidbar 15:23Bemidbar 30:2About R. Moshe Yitzchak Ashkenazi

Textual evidence that leaders may "add" and "detract" – These sources bring several verses as proof that leaders have the right to enact new laws (and, thus, that "לֹא תֹסֵף" does not apply to them):

• The Kuzari points to Devarim 17:9-11 or Devarim 18:18-19 which dictate that one must act according to what is directed by the priest, prophet or judge, implying that they have the authority to make new decrees.¹³  
• Hoil Moshe also points to Bemidbar 15:23 "אֵת כׇּל אֲשֶׁר צִוָּה י״י אֲלֵיכֶם בְּיַד מֹשֶׁה מִן הַיּוֹם אֲשֶׁר צִוָּה י״י וָהָלְאָה לְדֹרֹתֵיכֶם" as proof that, even after Moshe, laws can change (in accordance with what Hashem commands his prophets).

Why are leaders exempt from "לֹא תֹסֵף"?

• Unlikely to err – R. Yehuda HaLevi  explains that since these leaders are close to the Divine Presence, are blessed in both natural and acquired wisdom, often have some prophetic ability, and are checked by their peers, they are very unlikely to err.¹⁴ One cannot say the same about the masses.
• Oral tradition – Hoil Moshe suggests that already when given, many laws might have been accompanied by conditions and secret instructions which allowed for adaptation.¹⁵ These were relayed to the leaders of the time so that laws could be changed later when a future era necessitated or allowed for it.¹⁶ In other words, many later changes might be rooted in an oral tradition going back all the way to Moshe.

Limits to leaders' authority – Hoil Moshe places one limit on the ability of prophets and sages to innovate laws – that such laws do not affect the principles of faith or fundamentals of Torah.  However, he does not explain how one is to know what is included in such principles or who has the right to determine what these comprise.

Purpose of the law – These sources imply that the purpose of the law is to ensure that those who do not have sufficient knowledge do not make changes to the Torah which are not in line with Hashem's wishes.

Biblical cases – The Kuzari points to adjustments and new laws made by David, Shelomo and Ezra as evidence that such changes are permitted.

Rabbinic laws – This approach clearly allows for Rabbinic decrees, and does not limit these to those which are meant to safeguard existing commandments.  Any innovation which accords with the fundamentals of Torah is allowed.

Other potential cases of "לֹא תֹסֵף"

• Adding to existing laws – This approach might suggest that leaders are even allowed to change the form of an existing law (like adding a species to the lulav)¹⁷ or to mandate observing a law outside of its specified time (taking the four species on the eighth day).¹⁸
• Voluntary performance of a mitzvah – According to this approach, it would seem that if a layman on his/her own decides to take upon themselves an extra obligation, this might be considered a violation of "do not add".¹⁹  However, if the sages allow for such voluntary performance, it would then be permissible.

Fluidity of Torah – Hoil Moshe views Torah law as fluid and open to change, as long as such changes are made by sages who ensure that Torah's foundations remain intact. He notes that as people and times change, adaptations to the law become necessary. One generation might need a harsher penal code, while another might not yet be ready for certain laws.²⁰

Context – The law is found both at the beginning of Moshe' legal speech, an appropriate place to discuss who has the authority to make or change laws, and at the conclusion to Devarim 12, which speaks of the laws of "the place which Hashem shall choose".  As the Kuzari views this as the center of national leadership, emphasizing that specifically those whose authority stems from there alone have the ability to enact laws, it is logical that the law is mentioned in this context.

Polemics – R. Yehuda HaLevi mentions the Karaites explicitly and most of his comments appear to be directed at them.  He, thus, goes out of his way to both validate Rabbinic authority (which they reject) and to invalidate individual innovations or interpretations (a hallmark of Karaite commentary),²¹ especially those which affect the law.²²

Theological questions – This approach raises important theological questions:

• Replacing Torah? – If prophets are allowed to make or suspend laws at will, what is to stop an individual in the future from claiming prophetic authority and simply doing away with all of Torah?²³  This question might be what leads the Kuzari to consistently speak only of those leaders who are centered "בַּמָּקוֹם אֲשֶׁר יִבְחַר ה" and the Hoil Moshe to emphasize that all adjustments to Torah law must be in accordance with its fundamental principles.
• Can prophets and judges err?  If one assumes that they can, how is one to trust their innovations?²⁴ Moreover, how is one to even know who is a true or false prophet, worthy of being listened to?²⁵
• Is not Torah eternal?  Does not claiming that Torah law is fluid and that changes are allowed imply that the Torah is neither eternal nor perfect? Hoil Moshe might respond that additions to or detraction from Torah do not imply a lack of perfection in the Torah but rather in people. Though Hashem Himself does not change, people do, and it is they that necessitate change.²⁶

Limited to Mitzvah Details

The prohibition refers only to adding to or subtracting from the form or details of an already existing mitzvah, not to instituting new commands.

Sources:Sifre Devarim13:1About Sifre Devarim, RashiDevarim 4:2Eiruvin 96bEiruvin 96aRosh HaShanah 33aAbout R. Shelomo Yitzchaki, R. Yosef Bekhor ShorDevarim 4:2About R. Yosef Bekhor Shor, RaavadHilkhot Mamrim 2:9About R. Avraham b. David, ?MeiriBavli Rosh HaShanah 28bAbout R. Menachem HaMeiri?, perhaps Sefer HaChinukh454About Sefer HaChinukh,²⁷ R"Y Albo3:14About R. Yosef Albo, R. Shemuel EidelsMaharsha Chidushei Halakhot Rosh HaShanah 33aAbout R. Shemuel Eidels (Maharsha), R. Yosef BabadMinchat Chinukh 454About R. Yosef Babad (Minchat Chinnukh), ShadalDevarim 4:2Devarim 13:1About R. Shemuel David Luzzatto

Specifics of prohibition – Raavad asserts that the prohibition of "לֹא תֹסֵף" refers only to adding to existing positive commands.  One may not add or detract from the proscribed method of performing any positive directive.  He cites examples from the Sifre such as not adding or subtracting from the four species of the lulav,²⁸ four strands of tzitzit, or three priestly blessings.

Purpose of the law – Sefer HaChinukh asserts that one cannot change the form of Hashem's laws since they are complete and perfect as commanded.  Shadal elaborates that just because someone thinks an action will be pleasing to Hashem does not make it so, and thus one cannot decide on one's own to add to Hashem's command.  Moreover, innocent additions often unintentionally lead to problematic ones.²⁹

Relationship between "לֹא תֹסֵף" and "לֹא תִגְרַע"

• Elaboration – It is possible that these are not two distinct prohibitions but rather that the second phrase (לֹא תִגְרַע) comes to explain the first:
• R"Y Bekhor Shor asserts that the words "לֹא תִגְרַע" teach that it is prohibited to add to a law only if doing so will detract³⁰ from its intended observance.³¹
• Sefer HaChinukh, in contrast, implies that the verse is saying that due to the perfection of Hashem's laws' all additions to a mitzvah are by definition a detraction.³² [See below for the legal ramifications of these different readings.]
• Distinct prohibitions – This position could alternatively explain that each prohibition is distinct and simply the inverse of the other.  Just as one cannot add details, one cannot omit or lessen them.³³

What about Rabbinic laws? As "לֹא תֹסֵף" does not relate to enacting new laws and prohibitions, only to changing existing ones, Rabbinic decrees are not problematic. Adding prohibitions to safeguard the Torah is permitted³⁴ and even instituting new laws such as washing hands or making the holiday of Purim would not constitute a violation.³⁵

Other potential cases of "לֹא תֹסֵף"

• Extending the time frame of a mitzvah – According to R"Y Bekhor, since observing a mitzvah not in its proper time has no effect on and does not nullify the manner of the original observance, this would not be problematic.³⁶  According to Sefer HaChinukh, in contrast, any change to the mitzvah lessens it and so this, too, would be problematic.³⁷
• Performing a mitzvah multiple times – The same dispute might be relevant regarding repeatedly performing a mitzvah.
• Voluntary performance of a mitzvah – Since observing a command from which one is exempt does not change the nature of the law, this would not be a violation.³⁸
• Implying that a Rabbinic law is of Torah origin (or vice versa) – Raavad explicitly states that this is allowed.³⁹

Biblical Cases – ‏This position must explain several cases in Tanakh in which Biblical figures appear to add to or detract from existing positive commandments:⁴⁰

• Ezra's 1/3 shekel – This position might explain, as does RalbagNechemyah 10:33About R. Levi b. Gershom, that due to changes in currency, in Ezra's time a third of a shekel was equivalent in value to a Biblical half shekel and thus there was no change at all in the law.
• Shelomo's 14 day holiday – RashiMelakhim I 8:65About R. Shelomo Yitzchaki asserts that Shelomo did not celebrate Sukkot for two weeks, but celebrated the dedication of the Mikdash for seven days and the festival for seven says. This is supported by the description in Divrei HaYamim II 7:8 which mentions that the festival was observed for just seven days.⁴¹
• Extra lamps and tables in Mikdash – These sources might suggest that Torah speaks only of the vessels of the Tabernacle and nowhere mandates that the vessels of the Mikdash need be the same number or size.

Context – R"Y Albo suggests that, in context (Devarim 12-13),⁴² the prohibition constitutes a warning against adding Canaanite practices to one's worship of Hashem.⁴³ This, though, is simply a prototype laying out the nature of the law, which is understood to also apply to any similar case of adding to an existing practice.⁴⁴

Relationship between Devarim 4 and 13 – This position does not distinguish between the two.

Fluidity of Torah – R"Y Albo asserts that Hashem sometimes changes laws in accordance with the nation's needs, as evidenced within Torah itself. However, once the Torah was given through Moshe it has and will remain static, unless there is another Divine revelation as great as that at Mt. Sinai.

Includes Also Adding Mitzvot

The prohibition includes both adding to the details of a mitzvah and creating an entirely new one.

Sources:RambamMishneh Torah Minyan HaMitzvot ConclusionHilkhot Yesodei HaTorah 9:1-2Hilkhot Tefillah uBirkat Kohanim 14:12Hilkhot Mamrim 2:9About R. Moshe b. Maimon, RambanDevarim 4:2About R. Moshe b. Nachman, RalbagDevarim 4:2Melakhim I 8:65Nechemyah 10:33Devarim Toalot 4:2About R. Levi b. Gershom, Vilna GaonDevarim 13:1About R. Eliyahu of Vilna,  HaKetav VeHaKabbalahDevarim 4:2Devarim 13:1About R. Yaakov Mecklenburg, R. HIrschDevarim 4:2Devarim 13:1About R. Samson Raphael Hirsch, MalbimDevarim 4:2Esther 9:31About R. Meir Leibush Weiser, R. David Zvi HoffmannDevarim 4:2Devarim 13:1About R. David Zvi Hoffmann

Relationship between Devarim 4 and 13 – According to many of these sources,⁴⁵ each verse is the source for a different aspect of the prohibition:

• The Gr"A notes that the context of the prohibition in Devarim 4 is the directive to observe all the Torah's "laws and statutes".  Thus, the ensuing language of "לֹא תֹסִפוּ" refers to not adding another law to these.  In contrast, Devarim 13:1 opens, "אֵת כׇּל הַדָּבָר... אֹתוֹ תִשְׁמְרוּ לַעֲשׂוֹת", focusing on each individual commandment. The prohibition, then, teaches that every law must be observed in its proper manner, with no additions or subtractions.⁴⁶
• Rambam appears to learn out the laws in the opposite direction⁴⁷ but does not explain the choice.⁴⁸

What about Rabbinic laws? As these sources assume that this verse prohibits enacting new laws, they must explain the many Rabbinic decrees which appear to do exactly that:

• Ramban explains that Rabbinic safeguards are exceptional because the Torah itself commands that one put such fences in place.⁴⁹ New laws which are not meant to protect Torah law, however, might indeed be problematic.  Thus, for example, had the sages not found a source for Purim in the Torah,⁵⁰ its institution would have been a violation of "do not add."⁵¹
• Rambam, in contrast, asserts that the prohibition of "לֹא תֹסֵף" does not apply to all Rabbinic enactments, be they either safeguards or simple additions.  These are both permitted by Torah's directive to listen to Rabbinic authority (Devarim 17:11).  The prohibition of "לֹא תֹסֵף" forbids only presenting such decrees as Torah law and Divinely given.⁵² Purim, thus, is not problematic as it is clearly presented as a Rabbinically ordained holiday.
• Ralbag⁵³ learns that Rabbinic decrees are allowed from our verse itself. He suggests that the words "לֹא תֹסִפוּ... לִשְׁמֹר אֶת מִצְוֺת י״י" betray the goal of the law – to ensure proper observance.  As such, it is implied that any decrees made by the sages in an effort to either safeguard Torah or to preserve Torah values⁵⁴ are allowed.

Other potential cases of "לֹא תֹסֵף"

• Performing a mitzvah multiple times – This position might agree with RashbaRosh HaShanah 16aAbout R. Shelomo b. Aderet that fundamentally this, too, is a transgression of "do not add", as it is similar to adding a new command.⁵⁵  However, in cases where the extra performance is mandated by the sages as a safeguard or from doubt, there would be no violation.⁵⁶
• Observing a law outside of its mandated time – Ramban claims that lessening or extending the time frame of a mitzvah also falls under the prohibition⁵⁷ (if the individual was doing the act with the intent of observing a mitzvah).⁵⁸
• Voluntary performance of a mitzvah – This position might view this as a violation of the prohibition, especially if the individual viewed their performance as an actual obligation.  Cf. R. Yeshaya of TraniShibbolei HaLeketAbout R. Zidkiyah b. Avraham Anav (Shibbolei HaLeket) who states that though a woman may blow shofar, she may not do so with a blessing, as making a blessing indicates that she views this as an obligation and turns the action into a violation of "do not add."⁵⁹

Biblical Cases – These sources must explain the various Biblical cases in which someone either changes the form of  a command, suspends a law, or enacts a new one.

• Changes to a law – These sources could explain Shelomo's adding to the number of vessels in the Mikdash and Ezra's command to give a 1/3 shekel like the approach above.
• Suspending a law – Eliyahu's building of a private altar in an era when these were banned would be understood as a "הוראת שעה" rather than the annulment of a law.
• Enacting new laws – See the discussion above regarding Esther's instituting of Purim.

Purpose of the law – Ralbag explains that without the prohibition, it would be possible for the entire Torah to be lost.  If anyone can change, annul, or add laws as wished, the original Torah would no longer be recognizable. R. Hirsch adds that adjusting laws lessens the Divinity of Torah, turning it into a "forgery" as it moves from being a work of Divine perfection to one limited by human knowledge.⁶⁰

Context – R. Hirsch suggests that the context of the prohibition is a discussion of idolatry, to teach that subjectivity in observance, whereby one in effect equates one's own personal desires and decision making with God's commands, is equivalent to idolatry.

Fluidity of Torah – Rambam emphasizes the eternal and unchanging nature of Torah, pointing to the prohibitions of "לֹא תֹסֵף" as evidence. The perfection of Torah dictates that no additions or changes are ever necessary.⁶¹

Polemics – Rav Hirsch's equating of subjective observance with idolatry might be a reaction the Reform movement of his time.

Nonlegal in Nature

Moshe's words comprise general advice and rebuke rather than a legal ruling.

Sources:ChizkuniDevarim 4:2About R. Chizkiyah b. Manoach #1, perhaps

Context – These sources read Moshe's warning in the context of the rebuke of Chapters 1-3 which speak of the sin of the Spies which led to the deaths of the generation that left Egypt and postponing of entry into the land.

Specifics of rebuke

• Chizkuni presents Moshe as telling the nation that the reason they had not merited to enter the land was because they added to Hashem's command of "go and inherit" by asking to also send spies, and detracted from his later prohibition, "do not go up", by nonetheless attempting to enter.
• Or HaChayyim and Tzeror Hamor, instead, present Moshe as speaking of his own additions to Hashem's words, when he hit the rock rather than speaking to it. This led to his inability to enter the land, and so he cautions the nation not to err as he did.

According to both variations, Moshe's message is that the people do exactly as directed by Hashem "לְמַעַן תִּחְיוּ וּבָאתֶם וִירִשְׁתֶּם אֶת הָאָרֶץ".

"הַדָּבָר אֲשֶׁר אָנֹכִי מְצַוֶּה אֶתְכֶם" – According to this approach, Moshe's warning relates not to adding or detracting from Hashem's mitzvot but from even one time directives.

¹ Chizkuni does not elaborate upon what this would entail, writing only, "לא לגרוע מיראתו".  Today one might suggest that the verse warns against both polytheism and atheism, but it is doubtful whether atheism existed in the time of Tanakh.

² Cf. the commentary Keter Torah by the Karaite, Aharon b. Eliyahu, who explains that the prohibition of Devarim 13:1 relates to adding or detracting from any aspect of the sacrificial service (and not simply what one may offer as a sacrifice). He points to the nation's not lighting the lamps or offering incense in the time of Achaz (as described in Divrei HaYamim II 29:7) as an example of transgressing "do not detract".

³  Devarim 4 connects the prohibition with the sin of Baal Peor, while Devarim 13:1 follows a warning against imitating Canaanite idolatrous practices and precedes laws regarding those who incite to idolatry. [Chizkuni only mentions the context of Devarim 12, likely viewing 13:1 as forming a conclusion to that chapter, rather than an introduction to the next.]

⁴ Chizkuni only mentions the context of Devarim 12, likely viewing 13:1 as forming a conclusion to that chapter, rather than an introduction to the next.

⁵ He, too, views the verse as the conclusion to that chapter rather than an opening to Chapter 13.

⁶ The last verse of the chapter warns specifically against adopting cultic practices of surrounding nations such as child immolation.  This leads directly into the prohibition of not adding humans to the list of allowed sacrifices.

⁷ An example would be Esther's creating of a new holiday.

⁸ Thus, Eliyahu making an altar on Mt. Carmel in the period in which individual altars are forbidden would not be seen as an example of "do not detract"

⁹ See, for example, Ezra who appears to change the directive to give a half shekel donation, reducing the amount to 1/3.  [According to Ibn Ezra, in contrast, he actually increases the amount, mandating that the nation bring 1/3 a shekel in addition to the normal 1/2.].

¹⁰ This would include wearing phylacteries on Shabbat, or taking the four species on Shemini Atzeret.

¹¹ See the Karaite, Aharon b. Eliyahu (Keter Torah) on Devarim 4:2, who writes: "על כן בעלי הקבלה כשמוסיפין וגורעין עוברים במה שגזרה תורה ומוסיפין חטא על חטא."

¹² Though Chizkuni mentions both variations of the prohibition, he does not limit the derivation of each from just one verse.

¹³ He even goes as far as to suggest that the prohibition of "do not add" itself includes a prohibition that the masses can't add or detract from laws relayed not just by Hashem, but by any of their leaders.  [He understands the words "לֹא תֹסִפוּ עַל הַדָּבָר אֲשֶׁר אָנֹכִי מְצַוֶּה" to include not only commands that were relayed to the nation via Moshe, but those relayed by any valid prophet, priest, or judge from the Temple.]

¹⁴ Hoil Moshe, in contrast, does recognize that it is possible that even a sage might nonetheless err. See his commentsVayikra 16:8Vayikra 19:19Vayikra 24:19Bemidbar 15:23Bemidbar 30:2About R. Moshe Yitzchak Ashkenazi to Vayikra 19:19.

¹⁵ See his comments to Vayikra 16:8Vayikra 16:8Vayikra 19:19Vayikra 24:19Bemidbar 15:23Bemidbar 30:2About R. Moshe Yitzchak Ashkenazi, "ומי יודע מה דבר הורה משה רבנו בעל פה לנשיאי העדה וזקניה להודיע לבאים אחריהם בהתחלף מצב האומה ואמונותיה" or Bemidbar 30:2Vayikra 16:8Vayikra 19:19Vayikra 24:19Bemidbar 15:23Bemidbar 30:2About R. Moshe Yitzchak Ashkenazi, "אבל דבר בלתי מסופק הוא שלנשיאים הורה משה בדבר ה׳ בתורת סוד שבימים הבאים שֶׁיֵּרַךְ עורף העם יָקֵלּוּ מקושי המשפטים מבלי נטות מתורת ה׳ חלילה"

¹⁶ For example, Hoil Moshe suggests that the generation which left Egypt were in need of a harsh penal code and were thus commanded to literally pay an "eye for an eye". However, recognizing that later generations would not be in need of such severe punishments, the sages were permitted to later implement a lighter penalty, monetary compensation. [For further discussion, see "עַיִן תַּחַת עַיִן" – An Eye for an Eye].  He writes similarly regarding vows in his commentsBemidbar 30:2About R. Moshe Yitzchak Ashkenazi to Bemidbar 30:2.

¹⁷ It should be noted, however, that neither the Kuzari or Hoil Moshe actually say this.

¹⁸ These sources do not say this explicitly, but it would fit with the logic of the approach, which does not appear to limit the scope of leaders' changes.  Moreover, as the Kuzari notes that Shelomo was allowed to add to the number of vessels in the Mishkan and Ezra was able to change the 1/2 shekel donation into a 1/3 shekel contribution, he apparently thinks that leaders are permitted to change the form of an existing mitzvah.  [Thus, unless one assumes that specific changes are a rejection of a "principle of Torah", such adaptations should be allowed.]

¹⁹ However, it is also possible that these sources would not view this as "adding" to the Torah at all as the individual is not creating a new command nor claiming that their action constitutes a Torah command. [In such a case, these sources might nonetheless suggest that one should not make a blessing over such an action as saying a blessing might imply that the individual views the deed as an obligated action.]

²⁰ See the examples discussed in the above note. See also Hoil Moshe on slavery, "ואלו היה הדור ראוי, היתה אוסרת לגמרי לקנות עבד". [For further discussion, see Why Permit Slavery.]

²¹ Karaites place individual interpretation of Torah at the fore, believing that each person must determine for themselves the correct meaning of the commandments rather than relying on the interpretation of some centralized authority.  For the Kuzari they they are a prime example of the "masses" who have no authority and insufficient knowledge to do so.

²² He points to the debate between the Karaites and Rabbinate regarding the meaning of the words "ממחרת השבת" and the dating of the Omer, noting this as an example of where the masses have no authority to determine the law, whereas the priests,  judges and sages do. [For discussion of the debate, see MiMachorat HaShabbat[

²³ This paves the way for other religions such as Christianity or Islam to claim that their prophets, on the word of God, have annulled the Torah and replaced it with new laws.

²⁴ Considering that the Kuzari includes individuals such as Shelomo and David among those who are permitted to "add" or "detract", yet each of these sinned grievously, there would seem to be good reason to be wary of leaders' enactments.

²⁵ See Distinguishing Between True and False Prophets for discussion of this issue.

²⁶ Hoil Moshe, nonetheless, recognizes the dangers of his stance, and how it could be misinterpreted. He suggests that, for this reason, when the sages make changes to Torah laws they make sure to find a hook in the Torah so that the masses will not view the law as an innovation.
See his comments to Vayikra 24:19, "אבל סמכו דבריהם על המקרא לבלתי תת מקום לכופרים לומר שתורת ה׳ תתחלף לפי הזמנים, והיא במהותה טהורה עומדת לעד". See, similarly, what he writes on Bemidbar 30:2, "ורז״ל בשכלתם ובכונתם הטובה והנכונה הלכו בעקבו התורה, ופירשו הכתובים באופן שֶׁיֵּרָאֶה שלא נטו ממנה,"

²⁷ Sefer HaChinukh also brings Rambam's understanding of the mitzvah that it is prohibited to present a Rabbinic decree as if it  is mandated from the Torah, or to present a Torah law as if it is only Rabbinic in nature.  It seems, however, that his preferred understanding is that it relates only to adding to the details of already existing mitzvot.

²⁸ There is a dispute regarding whether this includes only adding a totally different species, or also adding more of each  (using 2 palm fronds rather than one).

²⁹ As an example he notes that if one person thinks there is no problem in offering a deer to God, someone else might suggest that a human, too, is fine. Many of the abominations of idolaters stemmed from customs which were themselves upright, but were eventually twisted into something else.

³⁰ See Chizkiyah's words in Bavli SanhedrinSanhedrin 29aAbout the Bavli who learns from Chavvah's understanding that it was not only forbidden to eat from the Tree of Knowledge but also to touch it, that all who add, detract.

³¹ For example, adding a fifth species to a lulav effectively nullifies the entire mitzvah, for it is never observed in its proper manner, and is thus prohibited. Celebrating a seven day holiday for eight days, on the other hand, would not be included in the prohibition, as the extra time does not detract from the original observance of the holiday.

³² Despite this reading of the verse, he nonetheless does count "לֹא תִגְרַע" and "לֹא תֹסֵף" as distinct commands.

³³ This appears to be the understanding of the Sifre and Rashi.

³⁴ In fact, if the purpose of the original prohibition is to maintain the perfection of Hashem's laws, adding such safeguards should even be encouraged.

³⁵ See Minchat Chikukh: "והנה כמה מצות שהוסיפו חכמינו זכרונם לברכה כגון נר חנוכה ונט״י וכדומה שהם דברים חדשים ולא הוסיפו במצות התורה נראה דודאי לא שייך ב״ת כי התורה נתנה רשות לחכמים לתקן תקנות הן בקום ועשה הן בשוא״ת לפי הזמנים".

³⁶ If one sits in a Sukkah after the holiday, it does not affect the observance of the original seven days which were done properly, so there is no "detraction".

³⁷ This is on condition that the individual was doing the action intending it to be a mitzvah. According to Sefer HaChinukh, a person who intends to celebrate an eighth day of a seven day festival is changing the nature of the mitzvah, as the holiday was meant to be observed for only seven days.

³⁸ See, though, Rashi on Bavli Rosh HaShanahRosh HaShanah 16a-16bRosh HaShanah 28bRosh HaShanah 33aAbout Bavli Rosh HaShanah who explains that R. Yehuda's position that women may not blow shofar is due to its being a violation of "do not add".  Cf. Ri in Tosafot Eiruvin Eiruvin 96aAbout Ba'alei HaTosafotwho disagrees, explaining that  that those who do not permit women to blow shofar, lay tefillin, and the like do not prohibit it due to the law of "do not add" but each for an individual reason. See also R. Shemuel EidelsMaharsha Chidushei Halakhot Rosh HaShanah 33aAbout R. Shemuel Eidels (Maharsha) who also questions Rashi and concludes that voluntary fulfillment of a mitzvah by women does not constitute a violation of "do not add", noting that this is not an expansion of an existing law and thus the prohibition does not apply.  Rabbenu Tam in Tosafot Rosh HaShanah 33a notes that the law is not like R. Yehuda in this case, also concluding that it is not problematic for women to perform voluntary time bound commandments.

³⁹ He writes that anything which is instituted as a "fence" to the Torah is not problematic, even if it was instituted for all times and  "עשאוהו כשל תורה וסמכוהו למקרא".

⁴⁰ Cases where an entire mitzvah is added (Esther's institution of Purim) or temporarily suspended (Eliyahu's sacrificing on a private altar) are not problematic as such actions would not be included in the prohibition of "do not add" according to this approach.

⁴¹ See RalbagMelakhim I 8:65About R. Levi b. Gershom who makes this point.

⁴² He does not address the context of the prohibition in Devarim 4 and how his reading would apply there.

⁴³ See the opinion of R"Y Kara above.

⁴⁴ See Shadal similarly.

⁴⁵ See Rambam, Vilna Gaon, HaKetav VeHaKabbalah, R. Hirsch, and R. David Zvi Hoffmann.

⁴⁶ HaKetav VeHaKabbalah and Hirsch point to another difference, the plural formulation of Devarim 4 (לֹא תֹסִפוּ) as opposed to the singular formulation (לֹא תֹסֵף) of Devarim 13. They suggest that the former implies that the warning is addressed to the nation as a whole, i.e. to the court system and sages who must ensure that they do not add new laws and pass them off as Torah law rather than Rabbinic safeguards.  The singular formulation of Devarim 13, on the other hand, implies that it is addressed to every individual in Israel, teaching them each not to change the form of existing laws.

⁴⁷ When speaking of not adding to or detracting from  the details of an existing law (Hilkhot Tefillah) he points to Devarim 4 as the source, while when speaking of the prohibition against adding new decrees and presenting them as Torah law, he cites Devarim 13.

⁴⁸ It is possible that he thinks that the plural formulation of Devarim 4 implies that the verse is directed at every single individual within the nation, warning each of them not to add to the form and details of mitzvot, while the singular formulation of Devarim 13 targets just the Sanhedrin, warning them not to pass off their decrees as Torah law. [Cf. HaKetav VeHaKabbalah and R. Hirsch in the above note, who point to this difference in formulation but reaches the opposite conclusion.]

⁴⁹ See verses such as Devarim 17:10-11 which give authority to judges and leaders and R. Kahana in Bavli YevamotYevamot 21aYevamot 90bAbout the Bavli who explains that Vayikra 18:30, "וּשְׁמַרְתֶּם אֶת מִשְׁמַרְתִּי" teaches that one must safeguard the Torah.

⁵⁰ See the discussion in Yerushalmi Megillah 1:5 and Bavli Megillah 14a.

⁵¹ He does not address the institution of Channukah, which would seem to be equally problematic. 

⁵² The opposite is prohibited as well.  One may not suggest that a Torah level prohibition is only a decree of the Rabbis.

⁵³ See R. Hirsch similarly.

⁵⁴ As such, instituting the holidays of Channukah and Purim whose purpose is to publicize Hashem's miracles and instill faith, a goal which is evident throughout Tanakh, is allowed.

⁵⁵ This, though, might be conditional on the person having intent to fulfill an obligation as he performed the mitzvah.

⁵⁶ Thus the Rabbinic institution of blowing the shofar an extra set of times (both while sitting and while standing) in order "to confuse the Satan" is not deemed problematic.

⁵⁷ Thus one cannot decide to celebrate Sukkot for only six days or, on the other hand, extend it to eight.

⁵⁸ Thus, if someone ate matzah after Pesach simply because they enjoy the taste, and not with intent to observe a command, this is not problematic.

⁵⁹ In other words, the Rid allows a woman to add a voluntary obligation as long as she makes it clear that she does not view it as obligatory.  This is somewhat similar to Rambam's understanding of "לֹא תֹסֵף", who views the prohibition as a means to ensure that one does not blur lines between Divine commands and those not Divinely commanded.

⁶⁰ See also SefornoDevarim 4:2Devarim 13:1About R. Ovadyah Seforno who notes the dangers of an individual deciding on his own to not observe a command, thinking that if the reason for the law does not apply to him, he has no reason to observe it. [He points to Shelomo's taking many wivesassuming that he would not be swayed by them to leave Torah, and yet he failed.]

⁶¹ As such, any prophet who were to come and introduce or annul a law in the name of Hashem, must be a false prophet.