Genesis 17:19-21

But God said, “No, but Sarah your wife will bear you a son, and you shall call his name Isaac; and I will establish My covenant with him for an everlasting covenant for his descendants after him. As for Ishmael, I have heard you; behold, I will bless him, and will make him fruitful and will multiply him exceedingly. He shall become the father of twelve princes, and I will make him a great nation. But My covenant I will establish with Isaac, whom Sarah will bear to you at this season next year.”