What is the ruling on one who swore an oath of divorce upon his wife that if she did not return in the morning, she would be divorced, then she returned the following day? What is the expiation for that? And is his wife divorced by that?

The husband's statement to his wife, "By Allah, you must return in the morning, and if you do not return, then do not come home again," is an ambiguous divorce (kinayah talāq). Divorce does not occur through it unless the husband intended it. If he intended it, then it is a conditional divorce that takes effect if the wife does not comply. If she does not return home in the morning, then one divorce has occurred. The wife is not unlawful to him unless she had been divorced twice before this. However, if he did not intend divorce, then the wife is not divorced.