God promised Abraham and Sarah that they would have a son

17 Abraham prostrated himself with his face on the ground to show respect to God. But then he laughed as he said to himself, “Can a man who is a 100 years old become a father of a son? And since Sarah is 90 years old, how can she bear a child?” 18 Then Abraham said to God, “Perhaps you will let Ishmael receive your blessing and inherit all I possess.” 19 Then God replied, “No! Your wife Sarah will bear a son for you. You must name him Isaac. I will establish my agreement with him, one which will be an everlasting agreement for him and his descendants. 20 As for Ishmael, I have heard what you asked me to do for him. I will bless him so that he also will have many descendants. Among his descendants will be rulers of twelve nations. And I will cause his descendants [MTY] to also become a great nation. 21 But Isaac, the son whom Sarah will give birth to at this time next year, is the one with whom I will establish my agreement.” 22 When God finished talking to Abraham, God disappeared from his sight.

23 On that same day, Abraham took his son Ishmael and all the males that were in his household, including the sons of all the slaves he had bought, and circumcised them. He cut off their foreskins, just as God told him to do. 24 Abraham was 99 years old when ◄he was circumcised/someone circumcised him►, 25 and Ishmael was thirteen years old when Abraham circumcised him. 26 On that very day Abraham and his son, Ishmael were circumcised. 27 And all the males in his household, the ones who had been born there and those who had been bought from foreigners, were also circumcised.