Leviticus 17:14, commentary and pictures

The prohibition forbids eating the blood of any manner of flesh, because the life of all flesh is in its blood and blood is sacred. It is perpetual, applying not only to beasts for sacrifice but to all cattle used for food. The restriction was given to preserve health and strength and to lessen the harmful results of eating animal food. Permitted animals had to be healthy and properly and carefully bled with the blood drained, blood and fat were forbidden, and animals that were torn or had died on their own could not be eaten.

If there had been no sin there would have been no shedding of blood, for bloodshed followed sin and the shedding of blood is connected with sin. The command preserves clear and definite ideas between the sacred and the common against the idolatrous practice of eagerly drinking the blood flowing from victims, which produced confused ideas. The blood of the slain victim symbolizes the blood of the Son of God, through whose shedding alone there can be atonement for sin, and the use of blood to cleanse the sanctuary from the sins of the people typifies the blood of Christ which alone can cleanse from sin. Israel regarded eating blood as sinful and shaped food customs around the prohibition, including care to drain blood from slaughtered animals. Because Gentiles used blood from sacrificed animals in food, eating together with them could offend Jewish Christians.

Saul's rash command forbidding food all day left his soldiers faint after a day of labor and fighting, and when the time of restriction until evening expired they rushed on the spoil and devoured flesh with the blood, breaking this law of God. Because Israel's ritual law forbade tasting blood, Christ's words about eating His flesh and drinking His blood were taken by some listeners literally and as sacrilegious.