What is the Shar'i ruling on a wife's refusal to work in her husband's father's nursery, and her refusal to return to him despite the husband's father swearing not to enter her house or the marital home as long as she is his son's wife, knowing that the wife is of good character, does not take financial compensation for her work, and the husband does not need her to work?

Your wife is not religiously obligated to work with your father, and she should not be pressured to do so. Your father erred in his oath. It is better for him to break his oath and offer expiation for it, based on the saying of the Prophet, peace and blessings be upon him: "Whoever takes an oath and then sees something better than it, let him do that which is better and expiate for his oath." We advise you to be dutiful to your father and to engage relatives or friends to gently advise him. If he does not change, then be patient with him and supplicate for him abundantly for guidance and rectitude.