Devarim 21:13

והסירה את שמלת שביה AND SHE SHALL REMOVE THE RAIMENT OF HER CAPTIVITY — the reason is because these are fine clothes, for the women of the heathen peoples adorned themselves in time of war in order to lure others (the enemy) to unchastity with them (Sifrei Devarim 213:1). וישבה בביתך AND SHE SHALL DWELL IN “THY” HOUSE — [not in the women’s apartments, but] in the house which he constantly uses: when he goes in he stumbles upon her, when he leaves he stumbles upon her (i.e. he cannot avoid meeting her constantly and the novelty of her beauty wears off); he sees her endless crying, sees her neglected appearance — and all this in order that she should become repulsive to him (Sifrei Devarim 213:2). ובכתה את אביה AND SHE SHALL WEEP FOR HER FATHER [AND HER MOTHER A FULL MONTH] — Why all this? In order to make a contrast — that while the Jewish woman (the captor’s Jewish wife) is gladsome, she should be downhearted, while the Jewish woman adorns herself, this one should bear a neglected appearance (Sifrei Devarim 213:5).

וְהֵסִ֩ירָה֩ אֶת־שִׂמְלַ֨ת שִׁבְיָ֜הּ מֵעָלֶ֗יהָ וְיָֽשְׁבָה֙ בְּבֵיתֶ֔ךָ וּבָ֥כְתָ֛ה אֶת־אָבִ֥יהָ וְאֶת־אִמָּ֖הּ יֶ֣רַח יָמִ֑ים וְאַ֨חַר כֵּ֜ן תָּב֤וֹא אֵלֶ֙יהָ֙ וּבְעַלְתָּ֔הּ וְהָיְתָ֥ה לְךָ֖ לְאִשָּֽׁה׃

and she shall put the raiment of her captivity from off her, and shall remain in thy house, and bewail her father and her mother a full month: and after that thou shalt go in to her, and be her husband, and she shall be thy wife.