What is the ruling on breaking an oath of divorce, and is expiation obligatory upon the husband if he swore by divorce against his wife that she would be divorced if she went to her sister's wedding?

In summary:

Nationality differences do not affect compatibility between spouses; what matters are religion and character. The father's action of preventing his wife and children from attending his sister's wedding due to the husband's differing nationality is unjustified. Regarding the suspended divorce oath, the ruling with us is that he cannot retract it, and if he violates it, his wife is divorced. This is the view of most scholars. However, Shaykh al-Islam Ibn Taymiyyah held that if he intended to effect a divorce, he can retract it, but if he intended a threat or prevention, the divorce does not occur, and he owes an expiation for a broken oath.