Blood

MAIMONIDES

"Blood was considered impure to men by the Tza'abah (pre-Islamic pagans) and still they ate it because they thought it was the food of demons and whenever anyone ate it, he could then co-operate with the demons... and there were people for whom eating blood was repulsive in their opinion... and they would slaughter an animal and catch the blood in some vessel or in a ditch and they would eat the meat of that slaughtered animal near its blood, and imagine that by doing so that the demons were eating the blood which is their food, and they would eat the meat... and the Torah came to those who recognized it, to remove these stubborn illnesses, and strengthened the prohibition of it (eating blood) as it did equally concerning idol worship: saying "and I will set My face against that person who eats the blood" (Lev. 17:10) just as it said about one who gives of his seed to Molech "and I will set My face against that man" (Lev. 20:6). This language is not found in any other commandment, only in idolatry and eating blood. And it considered blood to be pure and made it into a purifier of what ever touches it "and sprinkle it upon Aaron and upon his garments... and he shall be sanctified" (Ex. 29:21) (Guide to the Perplexed 3,46).

NAHMANIDES

Because God created all the lower beings for the needs of man, since he alone among them recognizes his creator. Nevertheless, he did not originally allow them to eat anything except plant life ... and after the Flood... He permitted them to slaughter animals... because their life is for man... but the life within them should provide atonement for man and be sacrificed before the Blessed One and not be eaten since no living creature can eat life itself because all the lives belong to God as do the lives of men (Commentary on Leviticus 17:11).

RAV KOOK

And the time of this conquest (conquering the instinct to eat meat) has not yet come... (therefore) sometimes meat will be used as food as the price of passage into a brighter era... This is the essence of morality when it is joined to its Divine Source, that it recognizes that there is a time for everything and sometimes it closes off its wellspring in order to gather strength for times to come ... thus the commandments concerning the eating of meat appeared in stages which lead to the highest goal ... The covering of the blood of beasts or fowl ... is the recognition of shame which is the beginning of moral healing "that you may remember and feel ashamed ... when I have forgiven you" (Ezekiel 16:63): Cover the blood, hide your shame! These deeds will bear their fruit, as time goes on the generations will be educated. The silent protest will, when its time comes, turn into roaring voice with a great magnificent sound and its way will succeed. (Talalei Orot, Hashkaphah al Ta'amei Hasmitzvot, Photocopy edition, Jerusalem, 1973, pp. 12-13)