Muwatta Imam Malik (Riwayat Yahya)

Imam Malik, may Allah have mercy on him, said: If a person owes a debt to another, and then the debtor says to the creditor: Leave your money with me as a mudarabah (profit-sharing investment), this is not permissible. Rather, the creditor should take back his money, and then he has the choice to give it as mudarabah or to keep it with himself, because if he enters into mudarabah before taking back his money, there is a suspicion of riba (usury) in it, as if the debtor has taken a delay and increased the debt.
Imam Malik, may Allah have mercy on him, said: If a person gave money to another as mudarabah, and then some of that money was lost before starting the trade, and then the mudarib (working partner) traded with the remaining money and earned profit, and now the mudarib wishes to consider the remaining amount after the loss as the capital, and whatever is more than that, to consider it as profit and divide it half and half, then this is not permissible. Rather, after completing the capital, whatever remains should be divided according to the agreed condition.
Imam Malik, may Allah have mercy on him, said: Mudarabah is not valid except with silver and gold, and it is not valid with goods and other things. However, in qirad (another form of partnership) and sales, if the corruption is minor and it is difficult to annul them, then they will be permissible, contrary to riba, which is forbidden whether it is little or much, and is never permissible in any way, because Allah, the Glorious and Exalted, says: "If you repent from riba, then you will get your principal amount; neither do wrong nor be wronged." __QUR_N__