Is the prize resulting from delivering the free purchase receipt to its rightful recipient, one of the poor, or to the shopper?

This prize belongs to the owner of the money, not the borrower, because it is a benefit derived from his money. This is also because profit is not deserved except through capital, labor, or guarantee. The borrower is an agent who is only authorized to act within the limits of the agency and in a manner most beneficial to his principal. He is not liable for losses unless there is misconduct. Therefore, if he is not liable for a decrease, he is not entitled to an increase, according to the Prophet's (peace and blessings be upon him) saying: "The gain follows the liability."