Genesis 17:17-24

17Then Abraham fell on his face and laughed and said to himself, "Shall a child be born to a man who is a hundred years old? Shall Sarah, who is ninety years old, bear a child?"

18And Abraham said to God, "Oh that Ishmael might live before you!"

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

20As for Ishmael, I have heard you; behold, I have blessed him and will make him fruitful and multiply him greatly. He shall father twelve princes, and I will make him into a great nation.

21But I will establish my covenant with Isaac, whom Sarah shall bear to you at this time next year."

22When he had finished talking with him, God went up from Abraham.

23Then Abraham took Ishmael his son and all those 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.