פּירוש אויף דברים 22:21

אל פתח בית אביה [THEN THEY SHALL BRING THE DAMSEL] TO THE ENTRANCE OF HER FATHER’S HOUSE — suggesting: “See what a child (lit., a plant) you have reared!” (Ketubot 45a).

they will stone her It is assumed that someone had sexual relations with her after she was betrothed (the fiancé presumably having betrothed her only upon her stating that she was a virgin). The Exegetes of our religion have interpreted these matters in exceedingly great detail [Ketubbot 44b ff]. The abovementioned “virginity” can be obtained only up to a certain time [Ketubbot 36a], depending on the biology of the young woman. Because of the word they shall stone her, this passage is connected to the case of the married woman, and subsequently the case of the betrothed woman.

לזנות בית אביה, there were witnesses that she had sexual intercourse after being betrothed.

אנשי עירה [AND] THE MEN OF HER CITY [SHALL OVERWHELM HER WITH STONES] — This means, the witnesses shall stone her, all the men of her city standing by (Sifrei Devarim 240:1; cf. Rashi on Leviticus 24:14).

לזנות בית אביה TO PLAY THE WHORE “IN” HER FATHER’S HOUSE — The word בית is equivalent to בבית.