Genesis 17:19-21

19But God said, “On the contrary, Sarah your wife will bear you a son and you must name him Isaac. So I will confirm My covenant with him as an everlasting covenant for his seed after him.

20As for Ishmael, I have heard you. See, I have blessed him and I will make him fruitful, and I will multiply him very very much. He will father twelve princes and I will make him a great nation.

21But My covenant will I establish with Isaac whom Sarah will bear to you at this set time next year.”