Difference between revisions of "Prohibition of Blood/2"

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<opinion>Sacredness of Life
 
<opinion>Sacredness of Life
 
<p>Refraining from eating blood, representative of an animal's vitality and soul, reminds one of the sanctity of all life. Eating it both demonstrates and invites cruelty.</p>
 
<p>Refraining from eating blood, representative of an animal's vitality and soul, reminds one of the sanctity of all life. Eating it both demonstrates and invites cruelty.</p>
<mekorot><multilink><a href="Jubilees6-1-21" data-aht="source">Jubilees</a><a href="Jubilees6-1-21" data-aht="source">6:1-21</a><a href="Jubilees7-24-45" data-aht="source">7:24-45</a><a href="Jubilees11-1-3" data-aht="source">11:1-3</a><a href="Jubilees21-1-25" data-aht="source">21:1-25</a><a href="Jubilees" data-aht="parshan">About Jubilees</a></multilink>,&#160;<multilink><a href="JosephusAntiquitiesoftheJews3-11-2" data-aht="source">Josephus</a><a href="JosephusAntiquitiesoftheJews1-3-8" data-aht="source">Antiquities of the Jews 1:3:8</a><a href="JosephusAntiquitiesoftheJews3-11-2" data-aht="source">Antiquities of the Jews 3:11:2</a><a href="Josephus" data-aht="parshan">About Josephus</a></multilink>, <multilink><a href="RambanVayikra17-11" data-aht="source">Ramban</a><a href="RambanBereshit1-29" data-aht="source">Bereshit 1:29</a><a href="RambanVayikra17-11" data-aht="source">Vayikra 17:11</a><a href="R. Moshe b. Nachman (Ramban, Nachmanides)" data-aht="parshan">About R. Moshe b. Nachman</a></multilink> #2,<fn>Ramban also speaks of the blood's detrimental effects on human nature and its being allocated to Hashem as reasons for the prohibition.</fn> <multilink><a href="SeferHaChinukh148" data-aht="source">Sefer HaChinukh</a><a href="SeferHaChinukh148" data-aht="source">148</a><a href="SeferHaChinukh187" data-aht="source">187</a><a href="Sefer HaChinukh" data-aht="parshan">About Sefer HaChinukh</a></multilink>,<fn>He also cites the Ramban regarding how eating of the animal's soul introduces animalistic traits into the human soul.</fn> <multilink><a href="AbarbanelVayikra17" data-aht="source">Abarbanel</a><a href="AbarbanelVayikra17" data-aht="source">Vayikra 17</a><a href="AbarbanelDevarim12-20" data-aht="source">Devarim 12:20</a><a href="R. Yitzchak Abarbanel" data-aht="parshan">About R. Yitzchak Abarbanel</a></multilink> #3,<fn>Abarbanel brings many reasons for the prohibition; this is the third possibility he raises in his commentary on Vayikra 17 and Devarim 12.</fn>&#160; <multilink><a href="KeliYekarVayikra17-13" data-aht="source">Keli Yekar</a><a href="KeliYekarVayikra17-13" data-aht="source">Vayikra 17:13</a><a href="R. Shelomo Ephraim Luntschitz (Keli Yekar)" data-aht="parshan">About R. Shelomo Ephraim Luntschitz</a></multilink>, <multilink><a href="ShadalDevarim12-23" data-aht="source">Shadal</a><a href="ShadalDevarim12-23" data-aht="source">Devarim 12:23</a><a href="R. Shemuel David Luzzatto (Shadal)" data-aht="parshan">About R. Shemuel David Luzzatto</a></multilink>,<fn>He also connects aspects of the prohibition to idolatrous practices.</fn> <multilink><a href="RDavidZviHoffmannDevarim12-23-25" data-aht="source">R. D"Z Hoffmann</a><a href="RDavidZviHoffmannVayikra3-17" data-aht="source">Vayikra 3:17</a><a href="RDavidZviHoffmannVayikra17-11-14" data-aht="source">Vayikra 17:11-14</a><a href="RDavidZviHoffmannDevarim12-23-25" data-aht="source">Devarim 12:23-25</a><a href="R. David Zvi Hoffmann" data-aht="parshan">About R. David Zvi Hoffmann</a></multilink> #2,<fn>See his comments to Devarim 12.&#160; In his commentary on Vayikra 3 and 17, R. Hoffmann also suggests that the prohibition relates to the fact that the blood is sanctified to Hashem.</fn> R. Kook</mekorot>
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<mekorot><multilink><a href="Jubilees6-1-21" data-aht="source">Jubilees</a><a href="Jubilees6-1-21" data-aht="source">6:1-21</a><a href="Jubilees7-24-45" data-aht="source">7:24-45</a><a href="Jubilees11-1-3" data-aht="source">11:1-3</a><a href="Jubilees21-1-25" data-aht="source">21:1-25</a><a href="Jubilees" data-aht="parshan">About Jubilees</a></multilink>,&#160;<multilink><a href="JosephusAntiquitiesoftheJews3-11-2" data-aht="source">Josephus</a><a href="JosephusAntiquitiesoftheJews1-3-8" data-aht="source">Antiquities of the Jews 1:3:8</a><a href="JosephusAntiquitiesoftheJews3-11-2" data-aht="source">Antiquities of the Jews 3:11:2</a><a href="Josephus" data-aht="parshan">About Josephus</a></multilink>, <multilink><a href="RambanVayikra17-11" data-aht="source">Ramban</a><a href="RambanBereshit1-29" data-aht="source">Bereshit 1:29</a><a href="RambanVayikra17-11" data-aht="source">Vayikra 17:11</a><a href="R. Moshe b. Nachman (Ramban, Nachmanides)" data-aht="parshan">About R. Moshe b. Nachman</a></multilink> #2,<fn>Ramban also speaks of the blood's detrimental effects on human nature and its being allocated to Hashem as reasons for the prohibition.</fn> <multilink><a href="SeferHaChinukh148" data-aht="source">Sefer HaChinukh</a><a href="SeferHaChinukh148" data-aht="source">148</a><a href="Sefer HaChinukh" data-aht="parshan">About Sefer HaChinukh</a></multilink>,<fn>He also cites the Ramban regarding how eating of the animal's soul introduces animalistic traits into the human soul.</fn> <multilink><a href="AbarbanelVayikra17" data-aht="source">Abarbanel</a><a href="AbarbanelVayikra17" data-aht="source">Vayikra 17</a><a href="AbarbanelDevarim12-20" data-aht="source">Devarim 12:20</a><a href="R. Yitzchak Abarbanel" data-aht="parshan">About R. Yitzchak Abarbanel</a></multilink> #3,<fn>Abarbanel brings many reasons for the prohibition; this is the third possibility he raises in his commentary on Vayikra 17 and Devarim 12.</fn>&#160; <multilink><a href="KeliYekarVayikra17-13" data-aht="source">Keli Yekar</a><a href="KeliYekarVayikra17-13" data-aht="source">Vayikra 17:13</a><a href="R. Shelomo Ephraim Luntschitz (Keli Yekar)" data-aht="parshan">About R. Shelomo Ephraim Luntschitz</a></multilink>, <multilink><a href="ShadalDevarim12-23" data-aht="source">Shadal</a><a href="ShadalDevarim12-23" data-aht="source">Devarim 12:23</a><a href="R. Shemuel David Luzzatto (Shadal)" data-aht="parshan">About R. Shemuel David Luzzatto</a></multilink>,<fn>He also connects aspects of the prohibition to idolatrous practices.</fn> <multilink><a href="RDavidZviHoffmannDevarim12-23-25" data-aht="source">R. D"Z Hoffmann</a><a href="RDavidZviHoffmannVayikra3-17" data-aht="source">Vayikra 3:17</a><a href="RDavidZviHoffmannVayikra17-11-14" data-aht="source">Vayikra 17:11-14</a><a href="RDavidZviHoffmannDevarim12-23-25" data-aht="source">Devarim 12:23-25</a><a href="R. David Zvi Hoffmann" data-aht="parshan">About R. David Zvi Hoffmann</a></multilink> #2,<fn>See his comments to Devarim 12.&#160; In his commentary on Vayikra 3 and 17, R. Hoffmann also suggests that the prohibition relates to the fact that the blood is sanctified to Hashem.</fn> R. Kook</mekorot>
 
<point><b>"כִּי הַדָּם הוּא הַנָּפֶשׁ"</b> – These sources point to this phrase as the basis for the prohibition.<fn>Variations of the phrase appear four times in <a href="Vayikra17-1-14" data-aht="source">Vayikra 17</a> (twice in verse 11 and twice in verse 14) and once more in <a href="Devarim12-16-25" data-aht="source">Devarim 12:23</a>, supporting the idea that Torah views this as a central component of the prohibition.</fn> They offer a variety of explanations as to the import of the fact that "blood is the soul":<br/>
 
<point><b>"כִּי הַדָּם הוּא הַנָּפֶשׁ"</b> – These sources point to this phrase as the basis for the prohibition.<fn>Variations of the phrase appear four times in <a href="Vayikra17-1-14" data-aht="source">Vayikra 17</a> (twice in verse 11 and twice in verse 14) and once more in <a href="Devarim12-16-25" data-aht="source">Devarim 12:23</a>, supporting the idea that Torah views this as a central component of the prohibition.</fn> They offer a variety of explanations as to the import of the fact that "blood is the soul":<br/>
 
<ul>
 
<ul>
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<point><b>Covering blood</b> – When it is not possible to sanctify the blood, as when a non-domesticated animal not fit to be sacrificed is killed, Hashem commands that the blood be covered instead. It is possible that this, too, is related to recognition of the sanctity of the animal's life and the cruelty inherent in taking it. <br/>
 
<point><b>Covering blood</b> – When it is not possible to sanctify the blood, as when a non-domesticated animal not fit to be sacrificed is killed, Hashem commands that the blood be covered instead. It is possible that this, too, is related to recognition of the sanctity of the animal's life and the cruelty inherent in taking it. <br/>
 
<ul>
 
<ul>
<li>In covering the blood, one admits to a degree of discomfort with the killing of animals and a recognition that though the deed is permitted, it should not be flaunted.<fn>Cf. R" Y Grossman, <a href="https://www.etzion.org.il/he/%D7%A4%D7%A8%D7%A9%D7%AA-%D7%90%D7%97%D7%A8%D7%99-%D7%9E%D7%95%D7%AA-%D7%93%D7%9D-%D7%95%D7%A8%D7%A6%D7%97-%D7%91%D7%A2%D7%9C%D7%99-%D7%97%D7%99%D7%99%D7%9D">דם ורצח בעלי חיים</a>, who points to the concept, prevalent in Tanakh, that spilled blood cries out for revenge.&#160; If covered, though, those cries cannot be heard.&#160;[See, for example, Bereshit 4:10, Yechezkel 24:7-8 and Iyyov 16:18.] As such, he suggests that here, too,covering the blood serves to prevent the innocent blood from "crying out" and quiets the call for blame.</fn></li>
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<li>In covering the blood, one admits to a degree of discomfort with the killing of animals and a recognition that though the deed is permitted, it should not be flaunted.<fn>See Sefer HaChinukh, "לפי שהנפש תלויה בדם... ולכן ראוי לנו לכסות הנפש ולהסתירו מעין רואיו טרם נאכל הבשר כי גם בה נקנה קצת אכזריות בנפשנו לאכל הבשר, והנפש נשפך לפנינו". Cf. R" Y Grossman, <a href="https://www.etzion.org.il/he/%D7%A4%D7%A8%D7%A9%D7%AA-%D7%90%D7%97%D7%A8%D7%99-%D7%9E%D7%95%D7%AA-%D7%93%D7%9D-%D7%95%D7%A8%D7%A6%D7%97-%D7%91%D7%A2%D7%9C%D7%99-%D7%97%D7%99%D7%99%D7%9D">דם ורצח בעלי חיים</a>, who points to the concept, prevalent in Tanakh, that spilled blood cries out for revenge.&#160; If covered, though, those cries cannot be heard.&#160;[See, for example, Bereshit 4:10, Yechezkel 24:7-8 and Iyyov 16:18.] As such, he suggests that here, too, covering the blood serves to prevent the innocent blood from "crying out" and quiets the call for blame.</fn></li>
 
<li>Rosenmuller (as brought by Shadal) suggests that covering the blood is a sign of respect, meant to ensure that this life source is not eaten even by animals.<fn>Cf. Netziv below who reads the act in the exact opposite manner, suggesting that it is a sign of disrespect and scorn.</fn></li>
 
<li>Rosenmuller (as brought by Shadal) suggests that covering the blood is a sign of respect, meant to ensure that this life source is not eaten even by animals.<fn>Cf. Netziv below who reads the act in the exact opposite manner, suggesting that it is a sign of disrespect and scorn.</fn></li>
 
<li>Hoil Moshe adds that even just seeing spilled blood leads the viewer to cruelty.<fn>He writes, "מחויבים לכסות גם כן דם הבהמה שלא יראה על פני האדמה ולא יאכזר הלבבות בראיתו, כי ראית הדם תכאיב לב טוב".</fn>&#160;</li>
 
<li>Hoil Moshe adds that even just seeing spilled blood leads the viewer to cruelty.<fn>He writes, "מחויבים לכסות גם כן דם הבהמה שלא יראה על פני האדמה ולא יאכזר הלבבות בראיתו, כי ראית הדם תכאיב לב טוב".</fn>&#160;</li>

Version as of 04:45, 26 April 2020

Prohibition of Blood

Exegetical Approaches

This topic has not yet undergone editorial review

Overview

Various reasons have been offered for the prohibition of blood. Many sources focus on the fact that blood represents the animal's life force and how its consumption both demonstrates and invites cruelty.  Eating the source of an animal's very vitality reflects a disregard for the sanctity of life and portrays callousness. Ramban adds that consuming an animal's blood is further dangerous to the individual himself, as the human soul will imbibe the negative characteristics of the animal soul.

Others focus not on how eating blood impacts man's behavior and nature, but its role in the worship of Hashem. Ibn Ezra claims that blood is off limits to man because it is dedicated to the altar and forms Hashem's portion of the sacrifice. R. D"Z Hoffmann, instead, points to the role played by blood in attaining atonement, pointing out that it would be inappropriate to consume that which aids one in achieving forgiveness.  Finally, Rambam asserts that the prohibition is one of many aimed at distancing man from idolatrous practices. As idolators would consume blood in an effort to divine the future, we are prohibited from doing so.

Blood is the Soul

Blood is prohibited from consumption because blood is symbolic of the animal's soul and life force. This position subdivides regarding why this is problematic:

Sacredness of Life

Refraining from eating blood, representative of an animal's vitality and soul, reminds one of the sanctity of all life. Eating it both demonstrates and invites cruelty.

"כִּי הַדָּם הוּא הַנָּפֶשׁ" – These sources point to this phrase as the basis for the prohibition.6 They offer a variety of explanations as to the import of the fact that "blood is the soul":
  • Similar to murder – Jubilees, drawing off the juxtaposition of the prohibitions regarding blood and murder in Bereshit 9:4-6, repeatedly links the two prohibitions,7 implying that the former is forbidden because it, too, is similar to taking a life.  Eating of an animal's blood/soul is like destroying its very vitality.8 
  • Similar to eating of a living being – Abarbanel likens the prohibition to that of "אבר מן החי", suggesting that eating flesh and blood is like eating of an animal while it is still alive. Shadal similarly suggests that the prohibition is aimed at preventing man from eating blood when it is still hot and flowing from the animal, "an act of immense cruelty".9
"וַאֲנִי נְתַתִּיו לָכֶם עַל הַמִּזְבֵּחַ לְכַפֵּר עַל נַפְשֹׁתֵיכֶם" – According to this approach, these words do not comprise the reason for the prohibition, but rather serve to complement it. The principle of the sanctity of life mandates that one not only refrain from eating blood, but also that one try to elevate any blood that has been spilled.  As such, the blood of sacrificed animals is sprinkled on the altar and used for atonement.11
Covering blood – When it is not possible to sanctify the blood, as when a non-domesticated animal not fit to be sacrificed is killed, Hashem commands that the blood be covered instead. It is possible that this, too, is related to recognition of the sanctity of the animal's life and the cruelty inherent in taking it.
  • In covering the blood, one admits to a degree of discomfort with the killing of animals and a recognition that though the deed is permitted, it should not be flaunted.12
  • Rosenmuller (as brought by Shadal) suggests that covering the blood is a sign of respect, meant to ensure that this life source is not eaten even by animals.13
  • Hoil Moshe adds that even just seeing spilled blood leads the viewer to cruelty.14 
It is not clear, though, according to any of these explanations, why there is no equivalent obligation to also cover the blood of domesticated animals eaten for pleasure (בשר תאווה).15
Scope of the prohibition – According to this approach, it is logical that the prohibition extends to all animals.    In fact, the Dead Sea Sect16 and Karaites maintain that even the blood of fish is prohibited.17
Context of Vayikra 17 – The first part of Chapter 17 mandates that, in the Wilderness Period,18 slaughtering animals for food was permitted only if the animal was brought as a sacrifice,19 and that transgression of this directive was considered spilling blood.  According to this approach, then, both halves of the chapter revolve around the same theme, the restrictions put on animal slaughter due the sanctity of animal life.20 Though an animal can be killed for food, wherever possible this must be done in a way that sanctifies the life taken, with the animal being offered as a sacrifice and its blood sprinkled on the altar.21
Prohibition to Noach – Jubilees, Josephus, and Ramban all understand the prohibition to Noach of ""אַךְ בָּשָׂר בְּנַפְשׁוֹ  דָמוֹ לֹא תֹאכֵלוּ" to refer to eating blood.  As soon as Hashem allowed consumption of animals,22 He simultaneously added the restriction that though the flesh may be eaten, the blood, symbolic of the soul, may not.23
Connection to fat – According to this approach, despite the juxtaposition in the verses, the reasons for the prohibitions of fat and blood are distinct.
Repetition and severity of the punishment – Torah's manifold warning against eating blood and the severity of the punishment is understood in light of this position's viewing it as akin to murder.24
"לְמַעַן יִיטַב לְךָ" – R. D"Z Hoffmann points to this reward as evidence that the prohibition is connected to prevention of cruelty. He notes that the phrase "לְמַעַן יִיטַב לְךָ" is found by only three specific commandments,25 the prohibition regarding blood, the directive to honor one's parents, and the obligation to send away a mother bird before taking her chicks.  Since the latter two cases involve acts of kindness and giving to another, R. Hoffmann suggests that there must be an element of kindness or preventing of cruelty in the fulfillment of the prohibition regarding blood as well.
"לֹא תֹאכְלוּ עַל הַדָּם" – These sources might view this as a distinct prohibition, related to the ban on eating blood only in that it, too, relates to recognition of blood as representative of life. Bavli Sanhedrin learns from the verse both that one cannot eat of even a properly slaughtered animal until its life has totally departed and that if a court sentences someone to death, the judges may not eat on the day of the execution. Each of these prohibitions, like that of eating blood, relates to the sanctity of life, both human and animal.

Mixing of Animal and Human Nature

Ingesting an animal's blood/soul introduces animal-like characteristics into the human soul.

"כִּי הַדָּם הוּא הַנָּפֶשׁ" – These sources point to this phrase as the basis for the prohibition. Ramban explains that an animal's blood/soul, as opposed to its flesh, can easily mingle with human blood.32  Thus, if the blood is consumed, the human soul will imbibe the negative characteristics of the animal soul.
Spiritual or physical danger
  • Spiritual – Most of these sources speak of the detrimental effects animal blood will have on humans in the spiritual realm, understanding that the blood will affect the human soul itself, introducing ugliness and lowering it to the level of animal.
  • Physical – Ralbag,33 in contrast, asserts that the blood affects one on a physical level.  Ingesting blood is difficult on the digestive system and harmful to the body.34
  • Both – Sefer HaChinukh combines these approaches, noting that blood is detrimental to the body, but since the body is the platform for the soul, when the body is harmed, the soul is affected as well.
"וַאֲנִי נְתַתִּיו לָכֶם עַל הַמִּזְבֵּחַ לְכַפֵּר עַל נַפְשֹׁתֵיכֶם" – According to R. Hirsch, the role played by blood in atonement is not a distinct reason for the prohibition, but integrally related to the need to prevent man from becoming animal-like. He explains that the fact that animal blood stands in for the human soul on the altar could have potentially led one to conclude that the human and animal souls are equal and that the latter is not harmful. To ensure that man recognize that this is not true, Hashem prohibited ingesting blood, announcing that the two are qualitatively different and that animal blood has no place in man.35
Covering versus spilling blood – These sources offer two (opposing) explanations for the difference in law between domesticated and undomesticated animals:
  • Blood more harmful – Netziv suggests that it is specifically the blood of wild animals which is covered since it is these animals who have the worst traits. Their blood, untamed and wild, deserves to be scorned and hidden from view.36
  • Blood less harmful – Akeidat Yitzchak, in contrast, suggests that the thinner blood of undomesticated animals might have led people to be less cautious in refraining from eating it, assuming that such blood is less likely to harm.  As such, a greater reminder was needed to show that it, too, is prohibited.
Scope of the prohibition – According to this approach, it is expected that the prohibition should relate to all animals, as all might introduce undesired qualities.37
Prohibition to Noach
  • According to Ibn Ezra, eating blood was already prohibited to Noach. When Hashem allowed meat to be eaten, He already prohibited its blood, knowing that its consumption is detrimental.
  • Seforno, in contrast, assumes that the command to Noach relates only to eating a limb or blood of a live animal.  Only the chosen Children of Israel were directed not to eat blood of even dead animals so as to protect their souls from absorbing any animalistic tendencies.
Parallels to fat and other forbidden foods – Sefer HaChinukh compares the prohibition of blood to other forbidden foods such as non-kosher animals or fat, maintaining that all are prohibited since they are harmful to the body or soul. [For elaboration, see Purpose of the Laws of Kashrut.]
"לֹא תֹאכְלוּ עַל הַדָּם" – According to this approach, this prohibition and its context of sorcery is unconnected to that of eating blood.
Repetition and severity of the punishment – The repeated warnings against ingesting blood might stem from the significant harm it can potentially cause the human soul.38

Sanctified to Hashem

Since the blood of animals is thrown on the altar and sanctified to Hashem, it is not fit for human consumption.

"וַאֲנִי נְתַתִּיו לָכֶם עַל הַמִּזְבֵּחַ לְכַפֵּר עַל נַפְשֹׁתֵיכֶם" – This verse forms the basis for this approach, but commentators focus on different aspects of it, leading to two related, but somewhat distinct understandings of the prohibition:
  • Apportioned to Hashem – According to Ibn Ezra, R"Y Bekhor Shor, and Ramban, the crucial point of the verse is that the blood is dedicated to the altar.41 Blood is off limits to man because it is Hashem's portion of the sacrifice (חלק גבוה).
  • Role in atonement – Ralbag, Abarbanel, and R. Hoffmann, instead, focus on the blood's role in atonement.
    • R. Hoffmann explains that if the animal's blood is supposed to represent and substitute for the sinner's soul, being sacrificed in the sinner's stead, it is inappropriate for it to be consumed.42
    • Ralbag adds that Hashem wanted to ensure that man recognize the atoning powers of blood so that he feel that his sacrifice was effective in achieving penance. As such, Hashem prohibited its consumption, highlighting its unique role.43
"כִּי הַדָּם הוּא הַנָּפֶשׁ" – According to this approach, this phrase comes to explain not why it is prohibited to eat blood, but why blood was chosen to serve as atonement and is sprinkled on the altar. Since blood represents or is the source of the animal's soul, it can represent man's soul and act as its substitute on the altar.
Why is blood of non-sacrificial meat prohibited? As only the blood of domesticated animals being offered as a sacrifice is sanctified to Hashem and used for atonement, this approach must explain why blood of "בשר תאווה"  (meat eaten for pleasure) and non domesticated animals and birds are also prohibited:
  • Safeguard – Ramban suggests that this is simply a safeguard to ensure that no one err and eat the blood of animals which can be sacrificed.
  • Distinct prohibition – R"Y Bekhor Shor and the Netziv,44 though, concede that this reasoning cannot account for the prohibition regarding non-domesticated animals and suggest that they are prohibited for other reasons.45
Spilling versus covering blood – These sources explain that since the blood of non-domesticated animals is not sprinkled on the altar, it was necessary to institute a different reminder that it is prohibited to eat of it and thus it is covered. No such reminder is necessary for domesticated animals eaten for pleasure, since those animals are associated with sacrifices and it is known that their blood in general serves to atone on the altar (even if in this particular instance the animal is being eaten).46
Prohibition to Noach – If the prohibition of blood is related to the sacrificial service and atonement, one might question why Noach was already commanded, "אַךְ בָּשָׂר בְּנַפְשׁוֹ דָמוֹ לֹא תֹאכֵלוּ" (Bereshit 9:4), centuries before the service was instituted:
  • Different prohibition – Most of these sources follow Bavli Sanhedrin 59aSanhedrin 59aAbout the Bavli and assume that the prohibition to Noach did not refer to eating blood but rather to  eating a limb from a live animal (אבר מן החי). 
  • Blood sacred even then – Ibn Ezra and Ramban, in contrast, understand that blood was already prohibited to Noach. If so, perhaps from the very first sacrifices brought by man, blood was already allotted to Hashem and not to man.47  
Connection to fat – Ibn Ezra, R"Y Bekhor Shor, and Ramban assume that the two prohibitions share a single explanation; both fat and blood are Hashem's portion and therefore prohibited to man.48  It is for this reason that the two prohibitions are often mentioned together.
Biblical parallels – R"Y Bekhor Shor compares the prohibition regarding blood to several other commandments which similarly stem from the fact that an object is sanctified to Hashem. He points to the prohibitions of making incense and the anointing oil or wearing wool and linen (a mixture reserved for priestly garments)49, pointing out that in all these cases "דהוה ליה כמשמש בשרביטו של מלך ואסור", it is as if one is using the scepter of the king and is prohibited.
General view of sacrifices – Ramban's understanding that the prohibition of blood is related to an inherently positive act, its being dedicated to Hashem, is consistent with his approach to sacrifices as a whole which he similarly views as inherently valuable and not instituted only to negate negative practices or beliefs. See Purpose of the Sacrifices for elaboration.
"לֹא תֹאכְלוּ עַל הַדָּם" – These sources suggest that this is a distinct prohibition and says nothing about not eating blood itself. Most, looking to the verse's immediate context of sorcery, relate it to idolatrous divination practices in which blood of an animal was spilled and a meal was eaten in the belief that this would invite demons who could foretell the future. This, however, has nothing to do with the general prohibition of eating blood.

Distancing from Idolatry

Consuming blood is prohibited since it is related to idolatrous practices.

Connection between blood and Idolatry – Rambam explains that idolaters would eat blood, believing it to be the nourishment of demons and that by participating with them in a meal, the demons would divine the future for them.
"לֹא תֹאכְלוּ עַל הַדָּם" – This approach suggests that the two prohibitions are intricately related. Rambam explains that those idolaters who found eating blood abhorrent would instead spill it into a vessel, eat around it, and invite the demons to the shared meal. Thus, it is prohibited not only to eat blood, but also to eat "on blood".  The ending of the verse, "לֹא תְנַחֲשׁוּ וְלֹא תְעוֹנֵנוּ", supports this reading as it, too, speaks of divination practices.
Context in Vayikra 17 – One of the advantages of this understanding is that it connects the two prohibitions of Vayikra 17, giving a common explanation for both. The first half of the chapter deals with the prohibition of slaughtering and sacrificing outside of the Mikdash, with the reason given being, "וְלֹא יִזְבְּחוּ עוֹד אֶת זִבְחֵיהֶם לַשְּׂעִירִם", lest the people come to sacrifice to goat-demons.  This is parallel to the reason for not eating blood, the subject of the second half of the chapter.
"וְנָתַתִּי פָנַי בַּנֶּפֶשׁ הָאֹכֶלֶת אֶת הַדָּם" – Rambam points to the language of the crime's punishment, "וְנָתַתִּי פָנַי בַּנֶּפֶשׁ הָאֹכֶלֶת אֶת הַדָּם" (Vayikra 17:10) as further proof of his understanding.  The phrase  "וְנָתַתִּי פָנַי בַּנֶּפֶשׁ/ בָּאִישׁ" appears only by three prohibitions: blood, necromancy, and worship of the Molekh, implying that the three are related, all being idolatrous in nature.51
"וַאֲנִי נְתַתִּיו לָכֶם עַל הַמִּזְבֵּחַ לְכַפֵּר עַל נַפְשֹׁתֵיכֶם" – This approach suggests that there is nothing intrinsically positive about sprinkling the blood on the altar; this is simply the safeguard to ensure that it not be used for idolatrous purposes.  Rambam further suggests that since idolaters viewed the blood as impure, Hashem wanted to disabuse people of this notion (and thus of blood's connection to demons). He, therefore, purified it and gave it a purifying role.52
Scope of the prohibition – According to this approach, it is logical that the prohibition includes the blood of both sacrificial and non-sacrificial animals as their blood, too, was used for idolatry.
Covering vs. spilling – The blood of non-domesticated animals is not only spilled but also covered to ensure that it is not used to invite demons.53  This is more necessary for their blood than for blood of animals eaten for pleasure since the latter were only permitted after arrival in Israel, at which point the lust for blood had mitigated somewhat.54  In addition, demons were believed to reside in the Wilderness and other barren areas, so it was more likely that non-domesticated animals killed in the wild would be used for such purposes than domesticated animals slaughtered in one's yard.
"כִּי הַדָּם הוּא הַנָּפֶשׁ" – Ramban questions this approach,55 pointing out that in explaining the prohibition, the Torah emphasizes the connection between blood and the soul, which this approach ignores. Ritvaספר זכרון לריטב"א פרק י' responds that these words explain why idolaters thought that blood was the food of demons to begin with.  It was specifically because of the blood's connection to the soul that they thought that the quasi-spiritual (and basically non-corporeal) demons ate of it.
Prohibition to Noach – One might question this approach from Hashem's prohibition to Noach, "אַךְ בָּשָׂר בְּנַפְשׁוֹ דָמוֹ לֹא תֹאכֵלוּ" (Bereshit 9:4), which appears to prohibit blood even in an era when no idolatry existed.56
  • This position might respond that this prohibition is related to  אבר מן החי rather than to eating blood. 
  • Ritvaספר הזיכרון לריטב״א פרק ט׳, instead, questions the assumption that there was no idolatry in Noach's generation. Even if previous idolators were wiped out in the flood, Hashem knew that it would not be long before others took their place.
General view of sacrifices – Rambam's approach to this prohibition is in line with his understanding of the sacrificial service as a whole. According to him, sacrifices (like the prohibition of blood) have no inherent value and are commanded only as a means to wean the nation from idolatry. See Purpose of the Sacrifices for elaboration.
"רַק חֲזַק לְבִלְתִּי אֲכֹל הַדָּם" – Devarim 12 warns, "רַק חֲזַק לְבִלְתִּי אֲכֹל הַדָּם". According to this approach there is a need to encourage the people to "be strong" and not eat of the blood since there was a real desire for it.57
Connection to fat – Rambam assumes that the prohibition of fat is related to health benefits rather than prevention of idolatry. The prohibitions might, nonetheless, be linked in the verses because blood, according to Rambam, is also somewhat unhealthy (even if this is not the main reason for its ban) or simply because both fat and blood are prohibited foods which happen to be sacrificed on the altar.58
Biblical parallels – Rambam is consistent in understanding many laws to be aimed at distancing the nation from idolatry.  See, for instance, his understanding of sacrifices, the Mishkan, the laws of hybrids, and Orlah.
Repetition and severity of the punishment – The Torah's many warning against eating blood stem from its connection to idolatry, one of the most serious offenses in Torah.