Rashi on Deuteronomy 22:23/רש"י על דברים כ״ב:כ״ג

1ומצאה איש בעיר [IF A DAMSEL THAT IS A VIRGIN BE BETROTHED UNTO A MAN] AND A MAN FIND HER IN THE CITY [AND LIE WITH HER] — (Because he found her outdoors) therefore he lay with her: a breach in the wall invites the thief; if she had remained at home (as becomes a chaste Jewish girl) this would not have happened to her (Sifrei Devarim 242:2-3).