What is the preponderant opinion regarding someone who told his wife, "You are unlawful to me if you reveal this secret," then she unintentionally revealed it, and does divorce occur, or is it considered an oath and a breach thereof, and what is the period for the return of the wife in the case of breach, and is the expiation (kaffara) on the husband or the wife?

If the wife reveals the secret forgetfully, without recalling the oath, then the husband does not violate his oath (does not "حنث") and nothing is incumbent upon him. However, if she reveals the secret intentionally, then the husband violates his oath. What results from violating the oath depends on the husband's intention behind the prohibition. If he intended divorce, then a divorce occurs. If he intended ẓihār (a form of divorce-like utterance), then it is ẓihār. If he intended an oath or did not intend anything specific, then he must offer expiation for an oath, which is: feeding ten needy persons or clothing them. If he cannot find them, then he must fast for three days. The expiation is incumbent upon the husband who took the oath, not the wife.