"and he has not taken her": (Scripture speaks of) a woman who is (halachically) fit for him — to exclude his divorcée (who had remarried), a widow betrothed to a high-priest, a divorcée or a chalutzah (a woman awaiting levirate marriage), betrothed to any Cohein, a mamzereth (a bastard, the issue of an illicit relationship) or a nathinah (a descendant of the Giveonites) betrothed to an Israelite, or an Israelitess betrothed to a nathin or a mamzer.
"let him go and return to his house": Let him heed the words of the Cohein and return. All of them (the returnees) heed the words of the Cohein at the battle formation and return and supply water and food for their brothers and repair the roads. Why were all these things stated? So that the cities of Israel not lie waste.