Is it permissible to eat from the parents' money if all of it is profit or capital from a corrupt speculation (mudarabah), or if there is another lawful income? And what is more befitting to do if the son is able to spend on himself? And will the mother's crying, anger, and displeasure harm the son if he abstains? And is it obligatory for the son to inform the father about the ruling on the money or the contract if it will cause severe anger?

A Muslim is not permitted to enter into a transaction whose ruling he does not know. A Mudarabah (profit-sharing partnership) in which the profit is a percentage of the capital is a void Mudarabah by scholarly consensus, because a condition for a valid Mudarabah is that the profit be a percentage of the profits, not of the capital.

In the event of a void Mudarabah, the profits belong to the owner of the capital, and the worker is entitled to an appropriate wage (ajr al-mithl) or an appropriate share (qirad al-mithl). The money given to parents from this void Mudarabah is not considered unlawful, and there is no justification for refraining from it. The legal ruling must be explained to the parents gently, kindly, and leniently, and one should supplicate for them and seek forgiveness for them if they do not accept.