Is a wife considered forbidden to her husband if he said to her: "By Allah, if you were to leave without my consent, you would be forbidden to me until I die," given that he does not recall his intention at the time, and is expiation required in this case?

The preponderant view regarding swearing by the unlawfulness of one's wife is that if divorce is intended thereby, then it is a divorce. If ẓihār (a pre-Islamic form of divorce by likening one's wife to one's mother) is intended, then it is ẓihār. If an oath is intended, or if nothing specific is intended, then it is an oath.

If the husband does not recall his intention, then the apparent ruling is that it is considered an oath, and he is obligated to perform an expiation for an oath (kaffārat yamīn), which is: feeding ten poor persons or clothing them. If he cannot find them, then fasting for three days.