Genesis 17:15-22 New Revised Standard Version (NRSV)
15 God said to Abraham, “As for Sarai your wife, you shall not call her 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 give rise to nations; kings of peoples shall come from her.” 17 Then 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?” 18 And Abraham said to God, “O that Ishmael might live in your sight!” 19 God said, “No, but your wife Sarah shall bear you a son, and you shall name him Isaac.[a] I will establish my covenant with him as an everlasting covenant for his offspring after him. 20 As 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. 21 But my covenant I will establish with Isaac, whom Sarah shall bear to you at this season next year.” 22 And when he had finished talking with him, God went up from Abraham.