In both legal and jurisprudential systems, commercial contracts—due to their dynamic and complex nature—frequently encounter challenges such as conceptual ambiguity and gaps in operational detail. On one hand, legal rules emphasize adherence to the written text and the explicit intent of the parties; on the other, the shifting realities of the market and the recurring practices of merchants necessitate mechanisms to discern the parties' true intentions. This research aims to elucidate the legal status and jurisprudential validity of custom (*urf*) as a source for legal inference—specifically for uncovering implicit intent and supplementing commercial contracts—thereby exploring how a balance can be struck between the stability of legal rules and the inherent flexibility of commerce. The central question concerns the role and validity of custom in the interpretation of commercial contracts, viewed through the lens of both jurisprudential principles and codified law. Furthermore, it addresses the hierarchy of precedence in the event of a conflict between the explicit terms of a contract, mandatory legal provisions, and established industry custom. Employing a descriptive-analytical method with a hybrid approach, this study examines the validity of custom within Imami jurisprudence by analyzing primary sources and principles such as "reliance on custom and "contextual exigencies" (*muqtadā al-ḥāl*). Subsequently, it investigates the status of custom within the hierarchy of interpretive sources by analyzing statutory law and judicial precedents. The findings indicate that, within both jurisprudential and legal frameworks, custom does not function as an independent or competing source, but rather as an interpretive and supplementary tool. From a jurisprudential perspective, custom holds a highly significant position in discerning the primary intent behind a contract, provided that it does not conflict with the general principles of *Sharia*.