Is it permissible for a married woman to take money from her husband without his knowledge to cover the travel expenses of her mahram for her to visit her family, if the husband is well-off and the mahram's financial circumstances do not allow him to bear the costs?

The basic principle is the inviolability of a Muslim's property unless it is given willingly by him. However, a wife is permitted to take from her husband's money, without his knowledge, for the obligatory expenses if he falls short in providing them. This includes food, clothing, medical treatment, and education. It does not include travel expenses to visit her family or the travel of her mahram (unmarriageable kin). This must be done within reasonable limits. A woman is not permitted to leave her husband's house except with his permission, even if it is to visit her parents.