Is a wife forbidden to her husband who vowed, "She is unlawful to me," as long as he has not returned the money he borrowed from her, then she relinquished the money after reconciliation, and then he had intercourse with her? And what is required of him?

If you declared your wife unlawful for yourself to pay off her debt, and then she absolved you of the debt and you had intercourse with her, there is no breaking of an oath (hanth) upon you, nor expiation, because the purpose of the oath, which was the absolution of the debt, has been achieved. However, do not repeat such oaths, for the saying "my wife is unlawful for me" is a reprehensible falsehood.