Genesis 17:15-21

God said to Abraham, “As for your wife Sarai, you will no longer call her Sarai. Her name will now be Sarah. I will bless her and even give you a son from her. I will bless her so that she will become nations, and kings of peoples will come from her.” Abraham fell on his face and laughed. He said to himself, Can a 100-year-old man become a father, or Sarah, a 90-year-old woman, have a child? To God Abraham said, “If only you would accept Ishmael!” But God said, “No, your wife Sarah will give birth to a son for you, and you will name him Isaac. I will set up my covenant with him and with his descendants after him as an enduring covenant. As for Ishmael, I’ve heard your request. I will bless him and make him fertile and give him many, many descendants. He will be the ancestor of twelve tribal leaders, and I will make a great nation of him. But I will set up my covenant with Isaac, who will be born to Sarah at this time next year.”