Genesis 17:17-21

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.”