Genesis 17:15-17

And God said unto Abraham, As for Sarai thy wife, thou shalt not call her name Sarai, but Sarah shall her name be. And I will bless her, and moreover I will give thee a son of her: yea, I will bless her, and she shall be a mother of nations; kings of peoples shall be of her. Then Abraham fell upon his face, and laughed, and said in his heart, Shall a child be born unto him that is a hundred years old? and shall Sarah, that is ninety years old, bear?