If the wife is of good religiosity and morals and she repented of her previous abuse of his mother, there is nothing wrong with keeping her provided that he offers
Kaffarah (expiation) for the oath he broke. The Kaffarah is to feed ten needy persons, clothe them or emancipate a believing bondsman. If he cannot do any of these things, he should fast for three days.May Allah grant us success. May Allah's Peace and Blessings be upon our Prophet Muhammad, his family and Companions!