Genesis 18:9-11

And they said unto him, Where is Sarah thy wife? And he said, Behold, in the tent. And he said, I will certainly return unto thee when the season cometh round; and, lo, Sarah thy wife shall have a son. And Sarah heard in the tent door, which was behind him. Now Abraham and Sarah were old, and well stricken in age; it had ceased to be with Sarah after the manner of women.