When delving into the purpose of the commandments related to the Sabbatical Year, many commentators seem to focus on either the account in Vayikra or those in Shemot and Devarim, and learn from one to the other. Thus, many understand from Vayikra 25 that Shemittah comes to teach the people about the sovereignty of Hashem and to trust in Him to provide for their needs. In contrast, Tzeror HaMor and others, drawing on Shemot 23, interpret all the laws as serving to promote social welfare and equality. The Rambam offers a third possibility, that the law is utilitarian, offering practical advice as to how to best care for the land. As none of these possibilities are mutually exclusive, it is possible that all three reasons together explain the commandment.
Recognition of Hashem
The Shemittah year reminds the nation of God's sovereignty and providence, makes them aware of their dependence upon Him, and requires a display of faith in Hashem.
"שַׁבָּת לַה'" – This position is grounded in the verses in Vayikra 25 which describe the Sabbatical Year as a Shabbat for Hashem specifically.2
Comparison to Shabbat – Many of these commentators3 point to the numerous parallels between the description of the Shemittah year and Shabbat, concluding that both serve as a reminder that Hashem created the world4 and that He is sovereign over it5 and all mankind:
Name – Both Shabbat Bereshit and the Shemittah year are referred to as a "Shabbat".6
Cycles of seven – Each of Shabbat and Shemittah revolve around cycles of seven, in which the first six units of time are devoted to labor (particularly, working the land) and the seventh to abstaining from it.
Rest for all – Both commandments emphasize the resting of the "slave and maidservant".
Extra on the sixth – Shadal notes that just as the Israelites received a double portion of manna on the sixth day of the week in anticipation of Shabbat, so too Hashem promises that the land will produce enough in the sixth year7 to sustain the nation through the Shemittah year.8
Juxtaposition – In Shemot 23, the two commandments follow one another, reinforcing their connection.
Break from work – All of these sources suggest that refrainingfrom tilling the land leads to a recognition of Hashem. They differ, though, in the their understanding of the process:
Time for Torah study – Ibn Ezra and R. Yosef Bekhor Shor9 emphasize that the break from work serves a practical function, giving people the time to delve into Hashem's Torah and devote themselves to Him.10
Dependence on Hashem – According to the Sefer HaChinnukh, the Akeidat Yitzchak, and the Keli Yekar, the lack of work teaches that it is not by man's strength alone that he succeeds, but rather due to God. To abstain from sowing requires extraordinary trust in Hashem, and deepens one's dependence upon and faith in Him.11
Land belongs to Hashem – The Keli Yekar and R. Hirsch points out that in refraining from work, people in effect relinquish their ownership on the land. This helps them recognize that they are mere renters from their "landlord", Hashem.12 Abarbanel similarly suggests that in imitating God's resting, we proclaim Him as Creator and owner of all. R. D"Z Hoffmann adds that the knowledge that the land belongs to Hashem should bring the nation to an awareness of the land's holiness and the proper conduct that such holiness requires.
Slaves to Hashem, not the land – The Sefer HaChinnukh and Akeidat Yitzchak assert that the Sabbatical Year is meant to prevent materialism and becoming enslaved to the land and work. Life should not be spent in pursuit of riches, but rather striving to follow the will of Hashem.
Produce free for the taking – This position focuses less on this aspect of Shemittah, but could find in it many of the lessons mentioned above. In leaving one's produce for all to partake, one remembers that it is God rather than man who owns everything. By sharing with all, one is also forced to suffice with less and not succumb to materialistic desires. Finally, in leaving one's food and being coupled with the poor, one recognizes that all of mankind is equally dependent on Hashem for sustenance.
Forgiving of debts – This approach might suggest that the canceling of all debts further highlights that all of one's possessions ultimately belong to Hashem.13
Punishment of exile
Ramban asserts that in not observing Shemittah one is in effect denying that Hashem created the world. Denying such a fundamental belief deserves harsh punishment.14
The choice of exile specifically might be seen as a measure for measure punishment. If man assumes that he, rather than God, is the true owner of the land, he needs to be expelled from it in order to learn his proper place.
R. D"Z Hoffmann adds that the holiness of Hashem's land requires its inhabitants to lead similarly holy lives. The land cannot bear a corrupt society, and thus as soon as the people begin to disdain the laws of Shemittah it will spit them out.
Due to the difficulties inherent in their observance,15 Shemittah and Yovel in effect serve as a litmus test of whether the nation believes in Hashem and is observing His commandments.
Blessing of the sixth year – While most commentators assume that the blessing involves increased production in the sixth year (see Nature of the Pre-Shemittah Blessing of the Produce), the Keli Yekar suggests that the same quantity is harvested as in a regular year, and the blessing is rather that the produce lasts for an extra year. According to him, observing Shemittah is an even more demanding test of faith, as the nation does not even receive and see a double portion beforehand, but must totally trust that Hashem will make the regular produce of the sixth year go further. This, he suggests, is similar to the test of the manna in which the Children of Israel could not save for the long term, but needed to have faith that Hashem would continue to provide for them.
Relationship to the Jubilee Year – This position suggests that the Jubilee Year, like Shemittah, brings the nation to recognition of Hashem.16 Land is returned to original owners not simply for social concerns, but to teach the nation that all land really belongs to Hashem ("כִּי לִי הָאָרֶץ"). The Keli Yekar adds that having two years in a row in which one must abstain from working the land provides one of the greatest lessons in trusting Hashem.
Parallel Commandments – Many other commandments have been understood to have a similar purpose. For instance, the bringing of first fruits and animals reinforces that all belongs to Hashem, while sitting in Sukkot reminds the people of God's constant providence during the wilderness years.17
The commandment comes to teach people to have mercy on those who are less fortunate and to emphasize the equality of all mankind before Hashem.
"וְאָכְלוּ אֶבְיֹנֵי עַמֶּךָ" – This position focuses on the sharing of one's produce with the poor and needy, as emphasized in Shemot 23.
Context – The verses that precede the commandment in Shemot similarly highlight the less fortunate, adjuring one not to oppress the foreigner.
Break from work
Lesson in empathy – R"A Saba suggests that normally the wealthy are complacent in the knowledge that they are well provided for, and rarely think of those who do not share this security. In the Shemittah year, when the rich are forced to abstain from working the land, they learn what it feels like to worry about providing for their families. This teaches them to empathize with the poor and to care for them, not only during the Shemittah year, but all the time.19
Equalizer – Shadal points to the equalizing aspect of having both rich and poor together refrain from work. When everyone rests together, the lines that separate the classes are blurred.
Produce free for the taking
Equate rich and poor – Shadal asserts that by forsaking one's produce, the socio-economic differences between rich and poor are reduced. For one year, all have the same rights to the crops in the field and all go together to collect their food.
Help the poor with dignity – R. Hirsch suggests that the Shemittah year allows the poor to obtain food with dignity. They are normally at the mercy of those wealthier than they, but now they can partake of produce without having to beg for it.
Forgiving of debts – The forgiving of debts plays the same equalizing role in an industrial society that forsaking of crops does in an agricultural one. In addition, in a sabbatical year, where the poor might be harder hit than the rich, cancellation of debts might be particularly helpful.
Freeing of Slaves – R. Yosef Bekhor Shor understands the commandment to free slaves in the seventh year ("וּבַשְּׁבִעִת יֵצֵא לַחָפְשִׁי") to refer to the Sabbatical Year rather than the seventh year after buying the slave. If so, this granting of freedom promotes another aspect of social equality.
Comparison to Shabbat – Shadal, like many of the commentators above, notes the many parallels between the commandments of Shabbat and Shemittah.20 He asserts that both serve to remind man that all are equal.
Relationship to the Jubilee Year – These commentators view the two commandments as working together and sharing the same goal. The returning of land and freeing of slaves21 in the Jubilee Year also serves to further social equality and care for the unfortunate.22
Punishment of exile – Exile and destruction as punishment for taking advantage of the poor and enslaved is attested to elsewhere as well. In Yirmeyahu 34, the prophet tells the nation that they will be killed by sword and plague and be taken to Babylonia for refusing to free their slaves in the seventh year.23
Capitalism versus socialism – Ze'ev Jabotinsky notes that the seven year Shemittah cycle and the Jubilee Year combine elements of both capitalism and socialism, allowing for checks and balances between the two systems. For six years a free market economy allows for growth and competition, while the seventh year tries to ensure that the pitfalls of such a system, i.e. big gaps between the rich and poor, are avoided.24
Caring for the Land
Shemittah serves a practical function in keeping the land healthy and capable of bearing fruit.
"שַׁבַּת שַׁבָּתוֹן יִהְיֶה לָאָרֶץ" – This approach emphasizes that Shemittah is a sabbatical year, not for Hashem or the nation, but for the land itself, as expressed in the verses in Vayikra 25 which speak of the year as a "שַׁבָּתוֹן... לָאָרֶץ".
Break from work – The ceasing from work serves a purely utilitarian function, to give the land time to rest and replenish its nutrients so that it can better produce in the future.
Produce free for the taking – This law might be viewed as a practical solution to the lack of food caused by not working the land. Everyone is entitled to take of the produce that grew, ensuring that all have what to eat.
Forgiving of debts – This law, too, is a practical one. During the Shemittah year, the poor might be more hard-pressed than usual, and so a special dispensation is made to cancel their debts.
Punishment of exile – The Akeidat Yitzchak, Abarbanel, and the Keli Yekar point out that the many warnings regarding the importance of Shemittah as well as the harsh punishment for its violators argue against the possibility that it was instituted solely for practical reasons. One would have thought that the land's lack of production itself would have been the offender's punishment rather than exile.
Are Hashem's commandments simply practical advice? This is not the only commandment that has been understood to be instituted for utilitarian purposes. The laws surrounding both kashrut26 and leprosy27 have been connected to promoting health, and the incense offering has been understood as a deodorizer to rid the Tabernacle of the odors of burnt animals and blood.28