Genesis 17:15

11You shall be circumcised in the flesh of your foreskin. It will be a token of the covenant between me and you.

12He who is eight days old shall be circumcised among you, every male throughout your generations, he who is born in the house, or bought with money from any foreigner who is not of your offspring.

13He who is born in your house, and he who is bought with your money, must be circumcised. My covenant shall be in your flesh for an everlasting covenant.

14The uncircumcised male who is not circumcised in the flesh of his foreskin, that soul shall be cut off from his people. He has broken my covenant.”

15God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but her name shall be Sarah.

16I will bless her, and moreover I will give you a son by her. Yes, I will bless her, and she will be a mother of nations. Kings of peoples will come from her.”

17Then Abraham fell on his face, and laughed, and said in his heart, “Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?”

18Abraham said to God, “Oh that Ishmael might live before you!”

19God said, “No, but Sarah, your wife, will bear you a son. You shall call his name Isaac. I will establish my covenant with him for an everlasting covenant for his offspring after him.