Rashi on Genesis 24:16/רש"י על בראשית כ״ד:ט״ז

1בתולה A VIRGIN — from the place of her hymen.

2ואיש לא ידעה AND A MAN DID NOT KNOW HER — not in its way (meaning, anally). Because the daughters of the nations would guard the place of their hymens, but abandon themselves from another place. It testifies about this one that she was clean from all [of this] (Genesis Rabbah 60:5).