Genesis 17:21

21 But my covenant I will establish with Isaac, whom Sarah shall bear to you at this season next year."

Genesis 17:21 In-Context

19 God said, "No, but your wife Sarah shall bear you a son, and you shall name him Isaac. I will establish my covenant with him as an everlasting covenant for his offspring after him.
20 As for Ishmael, I have heard you; I will bless him and make him fruitful and exceedingly numerous; he shall be the father of twelve princes, and I will make him a great nation.
21 But my covenant I will establish with Isaac, whom Sarah shall bear to you at this season next year."
22 And when he had finished talking with him, God went up from Abraham.
23 Then Abraham took his son Ishmael and all the slaves born in his house or bought with his money, every male among the men of Abraham's house, and he circumcised the flesh of their foreskins that very day, as God had said to him.
New Revised Standard Version Bible, copyright 1989, Division of Christian Education of the National Council of the Churches of Christ in the United States of America. Used by permission. All rights reserved.