Does the husband's statement to his wife: "You are forbidden to me like my mother," necessitate an expiation for breaking an oath (kaffarat yamin) or an expiation for Dhihar (kaffarat dhihar), especially since the husband claims not to remember the exact wording, while the wife insists on the truthfulness and certainty of her recollection of him uttering the phrase?

The correct view is that a man likening his wife to his mother, thereby prohibiting her to himself, is considered Zihar. This is the opinion of the Hanbalis, and Zihar is not established merely by the wife's claim unless there is evidence. If the wife is certain that Zihar has occurred, she must refrain from allowing him access to her until the husband performs the Kaffarah (definition) (expiation) for Zihar. This expiation is in sequential order: freeing a slave, and if he cannot find one, then fasting for two consecutive months, and if he is unable to do that, then feeding sixty poor people. There is no known basis for making the Kaffarah for Zihar an option (allowing choice), or for obliging the husband to perform the expiation for an oath when he does not remember.