Is the husband's travel without his wife's knowledge, in violation of her prior condition, considered an irrevocable divorce, or a single revocable divorce, or does the matter depend on the wife's decision, and does this entail expiation?

Divorce can only be initiated by the husband. If a wife stipulates to her husband that he must not travel without her knowledge, threatening him with divorce, and the husband accepts her condition, then the validity of the divorce depends on his intention. If he intended divorce, it occurs upon the fulfillment of the condition. If he did not intend divorce, it does not occur. If he intended to prevent himself from traveling but traveled forgetfully, divorce does not occur according to the more preponderant opinion. It would be a single revocable divorce if it was the first or second divorce.