15 And God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name.
16 I will bless her, and moreover, I will give you a son by her. I will bless her, and she shall become nations; kings of peoples shall come from her.”
17 Then 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?”
18 And Abraham said to God, “Oh that Ishmael might live before you!”
19 God 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.
20 As 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.
21 But I will establish my covenant with Isaac, whom Sarah shall bear to you at this time next year.”