Does the husband's saying to his wife, in a moment of anger, "I am fed up with you, and if I compare myself to my mother, I would compare myself to you," without saying "You are to me like my mother's back," constitute ẓihār, and what are its Sharīʿah implications, given that he was unaware of the ruling on ẓihār and the wife has passed away?

Ẓihār is when a legally responsible Muslim likens his wife, or a part of her, to the back of an unmarriageable female relative (maḥram), or a part of her. Its ruling is mentioned in Sūrat al-Mujādalah, verses 2-4. Phrases similar to ẓihār, such as "I am disgusted with you" or "if my soul is for my mother, my soul is for you," are considered metaphorical expressions (kināyāt) of ẓihār. Ẓihār occurs with these metaphorical expressions if the husband intended ẓihār; however, if he did not intend it, then it does not occur, based on the statement of Ibn Qudāmah that the intention determines whether it is ẓihār or not. Since the husband did not intend ẓihār in the mentioned case, ẓihār does not apply to him.