Genesis 17:19-21

But God said, “That’s not what I mean. Your wife, Sarah, will have a baby, a son. Name him Isaac (Laughter). I’ll establish my covenant with him and his descendants, a covenant that lasts forever. “And Ishmael? Yes, I heard your prayer for him. I’ll also bless him; I’ll make sure he has plenty of children—a huge family. He’ll father twelve princes; I’ll make him a great nation. But I’ll establish my covenant with Isaac whom Sarah will give you about this time next year.”