What is the ruling on one who said to his wife, "You are forbidden to me (haramt)," without intending divorce, knowing that this phrase is used to mean divorce in the custom of some societies? Does divorce occur, or is it considered an oath requiring expiation for a broken oath?

Prohibiting one's wife depends on the intention. If the husband intended divorce, or ẓihār, or an oath, then what he intended comes into effect. If it was a slip of the tongue and he did not intend the utterance at all, then nothing results from it. However, if he intended the word "prohibition," then what he intended comes into effect. If he did not intend anything, he is liable for an expiation for an oath (kaffārat yamīn).

The expiation for an oath is: feeding ten poor people, or clothing them, or freeing a slave. If he is unable to do any of these, then he moves to fasting for three days.