Is it obligatory to immediately repay my father's previous debt, or can we wait until the harvest season, noting that both projects are agricultural and follow the system of purchasing on credit and repaying upon crop production in Egypt?

May God have mercy on your father. We understand that your father has a debt that is due from an old project, and a deferred debt for a new project.

As for the immediate debt: Paying it from the inheritance after preparing the deceased is one of the most important rights, because it harms the deceased, and "the soul of a believer is suspended by his debt."

As for the deferred debt: Scholars have differed on whether it becomes due upon death or not. The Hanafis, Malikis, and Shafi'is held that it becomes due upon death and must be paid promptly, due to the impossibility of claiming it from the deceased, and the impermissibility of deferring it or making it contingent on specific assets, as this would harm both the deceased and the creditor. The Hanbalis (and this is their established position) held that deferred debt does not become due upon death if the heirs secure the debt with a pledge or a guarantor.

It is preferable and more cautious to promptly pay all of your father's debts. If this is not feasible, it is recommended to ask the creditors to transfer the debt to the heirs so that the father's responsibility is cleared.