“the life of the flesh is in the blood.” This general statement is true and was important in the sacrificial system of Israel. We know that the individual cells in the bodies of humans and animals are all alive, and “cellular death” is well understood in modern medicine. Nevertheless, the meaning of the phrase, “the life of the flesh is in the blood” is well understood, particularly as it applied in biblical times. The blood was necessary for life and without it the person or animal died, and that is as true today as it was in biblical times.
God had stated that the life was in the blood hundreds of years before Leviticus was penned. God had told it to Noah right after the Flood, when God first allowed humans to eat animals and not just plants (compare Gen. 1:29-30 with Gen. 9:3-4). The fact that the life of the flesh (the body) is in the blood made blood an acceptable substitute for the life of a person who deserved to die because of sin. The blood of the animal clearly depicted “a life for a life.”
“I have assigned it.” The Hebrew word translated “assigned” is literally “given,” but as John Hartley points out, when God is the subject as He is here, it “means ‘appoint, assign’” (Word Biblical Commentary. See also HCSB; NET; TNK). In making provision for covering people’s sin, God assigned the blood of an animal to be able to make atonement for people because the blood was the life of the flesh. But because of the importance of the blood in the sacrificial system, and particularly because it could cover for the deserved death of a human, God forbade eating animal blood. C. F. Keil writes: “God appointed the blood for the altar, as containing the soul of the animal, to be the medium of expiation for the soul of men, and therefore prohibited its being used as food” (Commentary on the Old Testament by Keil and Delitzsch). The point is that the life in the animal was poured out to cover, and thus preserve, the life of the person who sacrificed the animal. This is a case of “a life for a life,” although we know from the scope of Scripture that the death of the animal was only a temporary covering. It took the death of the Lord Jesus Christ to actually fully atone for the sins people commit.
“the life it has.” The addition, “it has” makes the text clearer to the English reader, but also narrower in scope. In total, the blood does not just “have” life, it supports and sustains life. Thus, the Hebrew, “because of the life,” is more complete than the English in the REV, but the more literal Hebrew is quite unclear and confusing to the reader.