Is taking profit from the merchant himself—in the event that the work with the money invested with him in the car spare parts trade ceases—considered usury (riba)?

It is permissible to give money to someone who trades with it, provided that the profit is shared between them according to their agreement. This transaction is called "Mudarabah" (profit-sharing). For Mudarabah to be permissible, it is stipulated that the worker (Mudarib) does not guarantee the capital except in cases of transgression or negligence. Furthermore, the profit share must not be a fixed amount or a percentage of the capital. Instead, it must be a common percentage of the actual profits, such as a quarter or a third, because specifying a fixed amount or a percentage of the capital transforms the transaction into Riba (usury). Therefore, if there are no profits, it is not permissible to take any profits. Such a transaction would be considered a stratagem to engage in Riba. Hence, it is necessary either to liquidate the partnership and withdraw the capital, or to ascertain the real profits and divide them. If there are no profits, then there is no right to the money that was taken.