Genesis 17:17-19

Abraham fell face down; he laughed and said to himself, ‘Will a son be born to a man a hundred years old? Will Sarah bear a child at the age of ninety?’ And Abraham said to God, ‘If only Ishmael might live under your blessing!’ Then God said, ‘Yes, but your wife Sarah will bear you a son, and you will call him Isaac. I will establish my covenant with him as an everlasting covenant for his descendants after him.