Genesis 17
16 Ref I will bless her, and moreover I will give you a son by her. Yes, I will bless her, and she will be a mother of nations. Kings of peoples will come from her."
17 Ref Then Abraham fell on his face, and laughed, and said in his heart, "Will a child be born to him who is one hundred years old? Will Sarah, who is ninety years old, give birth?"
18 Ref Abraham said to God, "Oh that Ishmael might live before you!"
19 Ref God said, "No, but Sarah, your wife, will bear you a son. You shall call his name Isaac.{Isaac means "he laughs."} I will establish my covenant with him for an everlasting covenant for his seed after him.