From Yale University Professor Christine Hayes:

The Noah story, the flood story, ends with the ushering in of a new era, and it is in many ways a second creation that mirrors the first creation in some important ways. But this time God realizes — and again this is where God’s got to punt all the time. This is what I love about the first part of Genesis — God is trying to figure out what he has made and what he has done, and he’s got to shift modes all the time — and God realizes that he’s going to have to make a concession. He’s going to have to make a concession to human weakness and the human desire to kill. And he’s going to have to rectify the circumstances that made his destruction of the earth necessary in the first place.

So he establishes a covenant with Noah: covenant. And humankind receives its first set of explicit laws, no more implicit, “Murder is bad.” “Oh I wish I had known!” Now we’re getting our first explicit set of laws and they’re universal in scope on the biblical writer’s view. They apply to all humanity not just Israel. So these are often referred to as the terms of the Noahide covenant. They apply to all humanity.

This covenant explicitly prohibits murder in Genesis 9, that is, the spilling of human blood. Blood is the symbol of life: that’s a connection that’s made elsewhere in the Bible. Leviticus 17[:11], “The life… is in the blood.” So blood is the biblical symbol for life, but God is going to make a concession to the human appetite for power and violence. Previously humans were to be vegetarian: Genesis 1, the portrait was one in which humans and animals did not compete for food, or consume one another. Humans were vegetarian. Now God is saying humans may kill animals to eat them. But even so, he says, the animal’s life is to be treated with reverence, and the blood which is the life essence must be poured out on the ground, returned to God, not consumed. So the animal may be eaten to satisfy the human hunger for flesh, but the life essence itself belongs to God. It must not be taken even if it’s for the purposes of nourishment. Genesis 9:4-6, you shall not eat flesh with its life, that is, its blood. For your lifeblood I will surely require a reckoning; of every beast I will require it and of humans… So if you are killed by a beast or a human, there will have to be a reckoning, an accounting. “…of every person’s brother I will require the life of the person. Whoever sheds the blood of a person, in exchange for that person shall his blood be shed, for God made humans in his image [Hayes translation]. All life, human and animal, is sacred to God. The covenant also entails God’s promise to restore the rhythm of life and nature and never again to destroy the earth. The rainbow is set up as a symbol of the eternal covenant, a token of the eternal reconciliation between the divine and human realms.

We should note that this notion, or this idea of a god who can even make and keep an eternal covenant is only possible on the view that God’s word and will are absolute, insusceptible to nullification by some superior power or some divine antagonist.