When is zakat due on partnership money that the principal received in installments a year after delivering it to the المضارب (Mudarib), and is he sinful for delaying the zakat for two years due to not possessing other money from which to pay the zakat?

If the land is sold for cash, the calculation of the hawl (zakat year) for the cash begins from the time of sale. Zakat is due on the profit generated from the invested capital (mudarabah) upon the completion of its hawl. If the mudarib (investing agent) returns a portion of the money after a year, you must pay zakat on it because its hawl has been completed. As for the remaining money that has not yet been returned, it is a debt owed by him. If the agent is solvent and you agree to grant him延迟 in repayment, the debt is subject to zakat as if it were in your possession. However, if he is insolvent or procrastinating, you are not obliged to pay zakat on it until you receive the debt, at which point you pay zakat on it once.