This paper examines how the 19th-century Damascene jurist Ibn 'Abidin is a key figure for studying the development of the Hanafi school from the medieval to early modern periods, not only because he revised persistent doctrines within the Hanafi school, but also because he brought the concept of ‘urf (customary practice) to the core of legal reasoning. Western scholarship on Ibn 'Abidin tends to view his contribution as lying outside of the juristic hierarchy and authority of the Hanafi school, if not as a rejection of the school’s authoritative structures. I demonstrate that Ibn 'Abidin never rejected the authoritative hierarchy of the school, but rather he acted in the name of its authority to justify departure from established opinions or admission of new rulings within its realm. I argue that to understand Ibn 'Abidin’s contribution is to acknowledge that the process of change within a legal school is intrinsic to its existence and a constitutive feature of its structure. I explore the doctrinal changes induced by internal mechanisms of the Hanafi legal school by focusing on two issues in the work of Ibn 'Abidin: (1) duress in contracts and (2) abstraction (ghasb) of property. Based on the legal devices of necessity (darura) and change in time and situation (ikhtilaf 'asr wa zaman), Ibn 'Abidin argues for a fundamental change in key Hanafi doctrines on duress and abstraction, transforming the medieval opinion of the school by calling on its eponym and founders. He contends – invoking the authority of Abu Hanifa who, “were [he] here, [he] would say the same [on this issue]” (Ibn 'Abidin, Majmu'at Rasa'il, 44) – that anyone, and not just a sultan, is capable of exercising coercion, and he shifts the opinion of the Hanafi school to accept the legal concept of abstraction of immovable property. Most importantly, Ibn 'Abidin negotiates the system of authoritative opinions of the school by introducing exceptions and invoking the general need of the public. This revision of key doctrines through the invocation of the very authorities Ibn 'Abidin seeks to protect has ramifications for the codification of Hanafi school in the 19th century that, I assert, extend to the codification of the Hanafi jurisprudence in the Mecelle, and is evident in his son’s participation on the Mecelle supervising committee.