Matthew Henry Commentary Genesis 9:4-7

"But flesh with the life thereof, [which is] the blood thereof, shall ye not eat. 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. Whoso sheddeth man`s blood, by man shall his blood be shed: For in the image of God made he man. And you, be ye fruitful, and multiply; Bring forth abundantly in the earth, and multiply therein." — Genesis 9:4-7 (ASV)

The main reason for forbidding the eating of blood was undoubtedly because the shedding of blood in sacrifices was to remind worshippers of the great atonement. Yet it also seems intended to check cruelty, so that people, by being accustomed to shed and feed upon the blood of animals, would not grow unfeeling toward them and be less shocked by the idea of shedding human blood.

A person must not take away their own life. Our lives belong to God, and we must only surrender them when He pleases. If we hasten our own death in any way, we are accountable to God for it. When God requires the life of a person from the one who took it away unjustly, the murderer cannot restore that life and therefore must forfeit their own instead. Sooner or later, in this world or in the next, God will uncover murders and punish those murders that are beyond human power to punish.

But there are those who are God's ministers to protect the innocent by being a terror to evildoers, and they must not bear the sword in vain (Romans 13:4). Willful murder ought always to be punished with death. To this law, a reason is added: such remains of God's image are still upon fallen humanity that whoever unjustly kills a person defaces God's image and dishonors Him.