Matthew Poole and continuators on Deuteronomy 21:13

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

(i. e.) Either 1 those goodly raiments in which she was when she was taken captive, in stead of which she now must put on a servile habit, as this is generally understood, or rather 2. those servile and sordid raiments which were put upon her when she was taken captive, as the manner was to do with captives, as the phrase it self seems to intimate, as prison-garments, Ier. 52. 33. are such garments as prisoners use to wear; and garments of praise are praise-worthy or glorious garments, and it seems harsh to call those garments of captivity, which are made for and generally worn by free persons onely, and which are usually taken away from persons when they come into captivity; Adde, that this doth not seem to be any part or token of her sorrow, but rather a mending of her condition, and exchanging her servile habit for a better and more decent one, which might be though this were a mourning habit.

Either their death, or, which was in effect the same, her final separation from them. Withall this signified her alienation from them or from their superstitious and Idolatrous courses, and her translation of her love from all other persons to her husband and to the true religion. Compare Psal. 45. 11.

Supposing what might very rationally be supposed of one in her circumstances, and what she signified by the foregoing rites, that she should submit to her husbands Religion, in which case the marriage might be tolerable. Or this was a permission and indulgence given to them for the hardness of their hearts, as in the case of Divorce, Deut. 24. 1. Mat. 19. 8.