What are the conditions for the validity of an assignment of debt?

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There are four conditions for the validity of an assignment of debt. The first condition is the equivalence (tamathul) of the two debts. Equivalence must hold in three aspects: the genus (e.g., gold for gold, silver for silver); the quality or description (e.g., uncirculated coins for uncirculated coins); and the timing of maturity (i.e., both debts must be due immediately or both must be deferred for the same period). If the two debts are immediately due, stipulating that the assignee will receive payment after a month invalidates the assignment because an immediate debt cannot be deferred. If these conditions are met, and the parties agree that the assigned party pays something better, or the assignee accepts less quality, or the deferred debtor agrees to expedite payment, or the immediate creditor agrees to a delay, it is permissible, as this is allowed in a loan context.