Genesis 17:15-19, 20-21

God continued speaking to Abraham, “And Sarai your wife: Don’t call her Sarai any longer; call her Sarah. I’ll bless her—yes! I’ll give you a son by her! Oh, how I’ll bless her! Nations will come from her; kings of nations will come from her.” Abraham fell flat on his face. And then he laughed, thinking, “Can a hundred-year-old man father a son? And can Sarah, at ninety years, have a baby?” Recovering, Abraham said to God, “Oh, keep Ishmael alive and well before you!” But God said, “That’s not what I mean. Your wife, Sarah, will have a baby, a son. Name him Isaac (Laughter). I’ll establish my covenant with him and his descendants, a covenant that lasts forever.

“And Ishmael? Yes, I heard your prayer for him. I’ll also bless him; I’ll make sure he has plenty of children—a huge family. He’ll father twelve princes; I’ll make him a great nation. But I’ll establish my covenant with Isaac whom Sarah will give you about this time next year.”