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 be a mother of 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, “O that Ishmael might live in thy sight!” 19 God said, “No, but Sarah your wife shall bear you a son, and you shall call his name Isaac.z I will establish my covenant with him as an everlasting covenant for his descendants after him. 20 As for Ishmael, I have heard you; behold, I will bless him and make him fruitful and multiply him exceedingly; he shall be the father of twelve princes, and I will make him a great nation. 21 But I will establish my covenant with Isaac, whom Sarah shall bear to you at this season next year.”