What is the ruling on the behavior of a wife who treats her husband's family with harshness and disrespects them, and what is the ruling on the oath of divorce uttered by the husband because of that?

An oath sworn by divorce is subject to the ruling of conditional divorce. Thus, if you break it, divorce occurs according to the majority of jurists, whether you intended divorce or not. Sheikh al-Islam Ibn Taymiyyah holds that if you did not intend divorce, then upon breaking the oath, you owe an expiation for an oath (kaffarat yameen). Therefore, if you do not fulfill what you swore upon, your wife is divorced according to the majority opinion. The husband is advised to exercise wisdom in disputes between his wife and his family, and the wife should treat her in-laws kindly to strengthen affection.