Genesis 17:15-22

God also said to Abraham: “Concerning your wife Sarai, you are not to call her Sarai anymore, but Sarah, ‘My Princess,’ will be her name. I will wonderfully bless her, and I will certainly give you a son through her. Yes, I will bless her greatly, and she will become a mother of nations; kings of nations will arise among her children!” Then Abraham laughed so hard he fell to the ground, saying to himself, “How in the world can a hundred-year-old man become a father? How can my wife Sarah get pregnant at ninety?” And then he spoke out loud: “O, that Ishmael might prosper with your blessing!” God said, “Listen to me. I promise that you and Sarah will have a son, and you will call him Isaac. I will confirm my everlasting covenant of love with him and his seed. And regarding Ishmael, I have heard your cry and I will indeed bless him. I will cause him to have many, many descendants. He will father twelve rulers, and I will make him into a great nation. But my everlasting covenant relationship is with Isaac, who will be born to you and Sarah about this time next year.” When he had finished speaking with Abraham, God ascended up to heaven.