If a father entrusts his son with his business, and then the son denies his father's money, is this money considered unlawful, and would the son's Hajj be accepted if he performs it with that money?

Islam emphasized the preservation of trusts and their return to their rightful owners, and prohibited their betrayal. The child must return to his father whatever business he entrusted him with; otherwise, he would be disobedient by taking someone else's money unjustly. As for performing Hajj with ill-gotten money, despite its unlawfulness, it does not affect the validity of the Hajj.