Does a wife become forbidden to her husband if she goes to her family's house without his knowledge, after her husband told her: "If you ever go to the university, and you don't go, and you go to your family's house without my knowledge, you will be forbidden to me," knowing that the husband is traveling and his father approved of her going to her family's house due to her mother's illness?

Scholars have differed concerning an oath to forbid one's wife. Some hold it to be ẓihār, some consider it a divorce, and others deem it an oath. The preponderant view is that it is interpreted according to the intention of the one who swore the oath. If he intended divorce, it occurs. If he intended ẓihār, it occurs. If he intended an oath, then an expiation for an oath (kaffārat yamīn) is due, and nothing else occurs.

If the husband intended to condition the forbiddance on his knowledge of and consent to your visit to your mother, then your going out without his knowledge and consent triggers what he intended by his oath.

You should know that the right to grant you permission rests with your husband, not with his father. A husband preventing his wife from visiting her sick mother without a valid reason is not his right and is considered a severance of kinship ties (qaṭʿ al-raḥim). Some scholars have even held that a judge may compel him to break his oath in this situation and rule for the wife to visit her parents, unless the prohibition is out of fear of harm.

It is advisable to involve someone influential with the husband to persuade him; otherwise, the wife may refer the matter to a Sharia judge.