Is the money that the husband took from his father—who does not treat his two wives equitably—and gave to his mother, lawful or unlawful, and must it be returned to his father?

The husband's action of taking money without his father's permission is considered an aggression against the rights of others and is forbidden, based on the Prophet's (peace be upon him) sayings: "Indeed, your blood, your wealth, and your honor are sacred among you," and "The wealth of a Muslim person is not lawful except with his willing consent." The father is not obligated to be just between his wives in additional gifts and grants as long as he provides the obligatory maintenance, as mentioned by Ibn Qudamah. The husband must return the money to his father or seek his forgiveness.