3, 4. When was the sanctity of blood introduced in the Scriptures, and on what principles does it rest?

³ Jehovah first disclosed the intimate connection between life and blood, as well as their sanctity, or sacredness, shortly after Cain murdered Abel. “Listen!” God said to Cain. “Your brother’s blood is crying out to me from the ground.” (Genesis 4:10) In Jehovah’s eyes, Abel’s blood represented his life, which had been brutally cut short. So, in a sense, Abel’s blood cried out to God for vengeance.​—Hebrews 12:24.

⁴ After the Noachian Flood, God gave humans permission to eat the flesh of animals but not the blood. God stated: “Only flesh with its life​—its blood—​you must not eat. Besides that, I will demand an accounting for your lifeblood.” (Genesis 9:4, 5) This command applies to all of Noah’s descendants right down to our day. It reaffirms what was implied in God’s earlier words to Cain​—that the life, or soul, of all creatures is represented by the blood. That decree also establishes that Jehovah, the Source of life, will hold to account all humans who disrespect life and blood.​—Psalm 36:9.

5, 6. How did the Mosaic Law show that blood is both sacred and precious? (See also the box “Respect the Life of Animals.”)

⁵ These two fundamental truths were reflected in the Mosaic Law. Leviticus 17:10, 11 reads: “If any man . . . eats any sort of blood, I will certainly set my face against the one who is eating the blood, and I will cut him off from among his people. For the life of the flesh is in the blood, and I myself have given it on the altar for you to make atonement for yourselves, because it is the blood that makes atonement by means of the life in it.”a​—See the box “The Atoning Power of Blood.”

⁶ If the blood of a slaughtered animal was not used on the altar, it was to be poured out on the ground. Thus, in a symbolic way, the life was returned to its original Owner. (Deuteronomy 12:16; Ezekiel 18:4) Note, though, that the Israelites did not have to go to extremes in trying to remove every trace of blood from the animal’s tissues. Provided that the creature was properly slaughtered and bled, an Israelite could eat it with a clear conscience, as due respect would have been accorded to the Life-Giver.

7. How did David show respect for the sanctity of blood?

⁷ David, “a man agreeable to [God’s] heart,” grasped the principles behind God’s law on blood. (Acts 13:22) On one occasion when he was very thirsty, three of his men forced their way into the enemy camp, drew water from a cistern, and brought it to him. How did David react? “Should I drink the blood of the men going at the risk of their lives?” he asked. In David’s eyes, the water was, in effect, the lifeblood of his men. So despite his thirst, he “poured it out to Jehovah.”​—2 Samuel 23:15-17.