15God said to Abraham, “As for Sarah your wife, you shall not call her Sarai, but Sarah shall be her name. 16I will bless her, and moreover I will give you a son by her. I will bless her, and she shall give rise to nations; kings of peoples shall come from her.” 17Then Abraham fell on his face and laughed, and said to himself, “Can a child be born to a man who is a hundred years old? Can Sarah, who is ninety years old, bear a child?” 18And Abraham said to God, “O that Ishmael might live in your sight!” 19God said, “No, but your wife Sarah shall bear you a son, and you shall name him Isaac. I will establish my covenant with him as an everlasting covenant for his offspring after him. 20As for Ishmael, I have heard you; I will bless him and make him fruitful and exceedingly numerous; he shall be the father of twelve princes, and I will make him a great nation. 21But my covenant I will establish with Isaac, whom Sarah shall bear to you at this season next year.” 22And when he had finished talking with him, God went up from Abraham.
23Then Abraham took his son Ishmael and all the slaves born in his house or bought with his money, every male among the men of Abraham’s house, and he circumcised the flesh of their foreskins that very day, as God had said to him. 24Abraham was ninety-nine years old when he was circumcised in the flesh of his foreskin. 25And his son Ishmael was thirteen years old when he was circumcised in the flesh of his foreskin. 26That very day Abraham and his son Ishmael were circumcised; 27and all the men of his house, slaves born in the house and those bought with money from a foreigner, were circumcised with him.