Genesis 17:19-21

God said, “No, Sarah your wife will have a son, and you will name him Isaac. I will make my agreement with him to be an agreement that continues forever with all his descendants. “As for Ishmael, I have heard you. I will bless him and give him many descendants. And I will cause their numbers to grow greatly. He will be the father of twelve great leaders, and I will make him into a great nation. But I will make my agreement with Isaac, the son whom Sarah will have at this same time next year.”