Deuteronomy 24:4 - Matthew Poole's English Annotations on the Holy Bible

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