15 God also said to Abraham, “As for Sarai your wife, you shall not call her by the name Sarai. Rather, Sarah is her name.
16 And I will bless her, and moreover, I will give you a son from her. I will bless her and she will give rise to nations. Kings of the peoples will come from her.”
17 Then Abraham fell on his face and laughed, and said to his heart, “Will a son be born to a 100-year-old man? Or will Sarah—who is 90 years old—give birth?”
18 So Abraham said to God, “If only Ishmael might live before you!”
19 But 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.
20 As 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.
21 But My covenant will I establish with Isaac whom Sarah will bear to you at this set time next year.”