Is the sponsor—whose debt was paid off by charitable individuals—entitled to keep the money he recovered from the debtor, or must he return it to the charitable individuals?

If the guaranteed person does not repay the debt and the guarantor is asked to pay, it is permissible to give the guarantor from zakat (definition) or charity to repay the debt on behalf of the guaranteed person. In this case, the guarantor does not have the right to demand from the guaranteed person what was paid. However, if the guarantor repays the debt from his own money, he has the right to demand repayment from the guaranteed person. If the guarantor is given money to repay the debt, he is not allowed to spend it on anything other than repaying the debt, even if he is poor.