Albert Barnes' Notes on the Whole Bible - Deuteronomy 21:12
The shaving the head (a customary sign of purification, Leviticus 14:8; Numbers 8:7), and the putting away “the garment of her captivity,” were designed to signify the translation of the woman from the state of a pagan and a slave to that of a wife among the covenant-people. Consistency required that she should “pare” (dress, compare 2 Samuel 19:24), not “suffer to grow,” her nails; and thus, so far as possible, lay aside everything belonging to her condition as an alien. read more
The Pulpit Commentary - Deuteronomy 21:13
The raiment of her captivity ; i . e . the raiment she had on whoa taken captive; this she was to lay aside, that she might put on garments of mourning. A full month ; literally, a month of days ; the period of mourning was forty days (cf. Genesis 50:3 ). read more