The principle of Istishab, originally developed in Imamiyyah jurisprudence to preserve a previous legal state in the face of doubt, has, over time, evolved into a key instrument for maintaining legal and social order. Drawing on Reinhart Koselleck’s theory of conceptual history, this study offers a multifaceted analysis of Istishab at three levels: jurisprudential, legal, and sociological. The findings reveal that Istishab not only holds a foundational place in Islamic jurisprudence, but also has a structural presence in Iran’s Civil Code and Code of Civil Procedure, playing a vital role in upholding acquired rights and guiding judicial decision-making. Furthermore, through concepts such as horizon of expectation, semantic accumulation, and institutionalization of meaning, the study explains how Istishab functions as a mechanism for fostering public trust, ensuring legal certainty, and managing social disputes. The historical-sociological analysis demonstrates that Istishab is not merely a tool for resolving doubt, but a model for reproducing order within diverse political, legal, and cultural contexts. Taking an interdisciplinary approach, this research seeks to highlight the often-overlooked connection between jurisprudential rationality and the social function of legal principles.