‌Context & Objective: The flexibility of the Islamic legal system allows for complex transactional structures such as the combination of sale and lease contracts within a single creation. While Shia jurisprudence generally accepts the validity of combining two independent contracts based on general principles of contract law and consensus a fundamental tension arises when such combinations intersect with mandatory rules like the prohibition of usury or riba. This article investigates the legal nature of combined contracts to determine whether a lease component can serve as a riba-nullifying supplement for a concurrently executed sale. The research specifically addresses whether the formal legality of combining contracts can substantively override the prohibition of riba in cases where the sale portion involves usurious elements.
 ‌Method & Approach: This study utilizes a doctrinal research methodology to dissect the jurisprudential foundations of combined contracts and the conditions under which a supplement effectively nullifies riba. The analysis employs the theory of dissolution which posits that a single expression of will can be analytically decomposed into multiple independent legal entities. Furthermore, the research applies the rule of price apportionment to demonstrate how a unified consideration is distributed among contract components based on market value. To validate the inherent independence of these components the study uses the argument of multiple owners as a logical test to distinguish between formal and substantive joinder.
 ‌Findings: The research identifies a fundamental distinction between a commodity supplement (joining property to property) and a contractual supplement (joining one contract to another). A commodity supplement effectively changes the subject of sale into a composite item thereby removing the transaction from the scope of riba rules. Conversely a contractual supplement such as a lease remains inherently independent and fails to modify the subject matter of the sale portion. The findings demonstrate that because the lease and sale maintain distinct legal identities the lease cannot function as a riba-nullifying agent. Moreover, legal instruments like price apportionment ensure that mandatory rules such as the requirement for immediate possession in certain sales or the prohibition of riba are applied strictly to the relevant component without being diluted by the accompanying contract.
 ‌Conclusion: Ultimately the study concludes that adding a secondary contract to a primary one does not alter the essential legal identity or the application of mandatory religious prohibitions. In the event that the sale portion of a combined contract is found to be usurious the presence of a lease contract cannot render the transaction valid. These findings highlight a broader jurisprudential priority of substantive legal content over contractual form within Imami law. Practically this distinction provides a critical framework for evaluating modern Islamic banking and finance instruments ensuring that complex financial structures represent genuine asset-based transactions rather than mere formal covers for usurious debt.