What is the ruling on one who has intercourse with his wife after swearing that she would be unlawful to him until her father returns from a four-month journey, and does the expiation (kaffarah) become void upon the return of her father or not?

Prohibiting one's wife depends on the husband's intention: if he intended divorce, it constitutes a divorce. Specifying a time for it does not prevent its occurrence; the time limit is nullified, and the divorce becomes absolute. Reconciling is permissible before the 'iddah (waiting period) ends, provided it does not complete three divorces. If he intended ẓihār (a form of divorce by injurious comparison), it constitutes a temporary ẓihār, according to the preponderant opinion, and the expiation for ẓihār becomes obligatory and is not waived by the return of the wife's father. It must be paid before conjugal relations with the wife. If he intended an oath or did not intend anything, an expiation for an oath becomes obligatory.