What is the ruling on taking money from people on the day of the henna ceremony and the wedding, and must it be returned? And what should the children do if the one who took the money dies and they do not know whether he repaid it or not?

If the prevailing custom indicates that what was given was intended as a repayment for its equivalent, then it is a debt that must be repaid. It is not forfeited by the death of the recipient; rather, it must be settled from his estate before its division. If the deceased did not leave an inheritance, then the heirs are not obligated to repay the debt from their own funds. However, it is commendable for them to do so if they are able, as an act of kindness to the deceased and to clear his conscience.