God blessed Noah and his sons and said to them, “Be fruitful and multiply and fill the earth. The fear and terror of you will be in every living creature on the earth, every bird of the sky, every creature that crawls on the ground, and all the fish of the sea. They are placed under your authority. Every living creature will be food for you; as ⌊I gave⌋ the green plants, I have given you everything. However, you must not eat meat with its lifeblood in it. I will require the life of every animal and every man for your life and your blood. I will require the life of each man’s brother for a man’s life.
Whoever sheds man’s blood,
his blood will be shed by man,
for God made man
in His image.
But you, be fruitful and multiply; spread out over the earth and multiply on it.” (Genesis 9:1-7)
From the time of Adam until Noah’s flood, everyone was a vegetarian. God had judged the world, wiping out most of the human race and most of the animals. After the rain stopped and the water went down, Noah, his family, and the animals left the ark.
God then made a covenant—a contract—with those who had survived. God told them some old things and some new things. They were to repopulate the world—the same thing God had told Adam and Eve. Then there was a twist on an old thing: Adam and Eve had been given all the plants to eat, with one restriction: they could not eat from the Tree of the Knowledge of Good and Evil. Now, after the flood, God told Noah and his family that from then on, in addition to all the plants, they could eat all the animals, too. There was only one restriction: they could not eat the blood.
Likewise, the blood of human beings was not to be shed: anyone, whether human or animal, who took the life of a human being would forfeit his own life, because human beings were created in the image of God.