Genesis 17:15-17

Then God said to Abraham, “As for Sarai your wife, you shall not call her name Sarai, but Sarah shall be her name. And I will bless her and also give you a son by her; then I will bless her, and she shall be a mother of nations; kings of peoples shall be from her.” Then Abraham fell on his face and laughed, and said in his heart, “Shall a child be born to a man who is one hundred years old? And shall Sarah, who is ninety years old, bear a child?”