John Wesley on Deuteronomy 24:4

May not - This is the punishment of his levity and injustice in putting her away without sufficient cause, which by this offer he now acknowledgeth. Defiled - Not absolutely, as if her second marriage were a sin, but with respect to her first husband, to whom she is as a defiled or unclean woman, that is, forbidden things; forbidden are accounted and called unclean, Jud 13:7, because they may no more be touched or used than an unclean thing. Thou shalt not cause the land to sin - Thou shalt not suffer such lightness to be practised, lest the people be polluted, and the land defiled and accursed by that means.