John Calvin Commentary Genesis 9:5

"And surely your blood, [the blood] of your lives, will I require; At the hand of every beast will I require it. And at the hand of man, even at the hand of every man`s brother, will I require the life of man." — Genesis 9:5 (ASV)

And surely your blood of your lives will I require. In these words, the Lord more explicitly declares that He does not forbid the use of blood out of regard for animals themselves, but because He considers the life of humans precious, and because the sole purpose of His law is to promote common humanity among them.

I therefore think that Jerome, in rendering the particle אך (ach,) for, has done better than those who read it as an adversative disjunctive: ‘otherwise your blood will I require.’ Yet literally, it may best be translated this way: ‘And truly your blood.’ In my opinion, the whole context should be read as follows: ‘And truly your blood, which is in your lives, or which is as your lives, that is, which gives life and animates you, regarding your body, will I require: from the hand of all animals will require it; from the hand of man, from the hand, I say, of man, his brother, will I require the life of man.’ The distinction by which the Jews define four kinds of homicide is trivial; for I have explained the simple and true meaning, namely, that God values our life so highly that He will not allow murder to go unavenged.

And He stresses this with so many words, so that He may make the cruelty of those who lay violent hands on their neighbors all the more detestable. And it is a significant proof of God’s love toward us, that He undertakes the defense of our lives and declares that He will be the avenger of our death.

In saying that He will exact punishment from animals for the violated life of humans, He gives us this as an example. For if, on behalf of humans, He is angry with brute creatures who are driven by a blind impulse to feed on them, what, do we suppose, will become of the person who, unjustly, cruelly, and contrary to the sense of nature, attacks his brother?