This article introduces the legal methodology of independent mujtahid (legal scholar) Abu Bakr ibn al-Mundhir al-Naysaburi (d. 930) in order to shed light on the nature of ijtihād (independent judgment in a legal or theological question) on the eve of crystallization of the four Sunni legal schools. Ibn al-Mundhir's presentation of laws concerning punishment for theft indicates that the Qurʿan and Prophetic hadith played a modest role in early elaboration of Islamic law. Instead, the bulk of this early mujtahid's efforts were devoted to culling and evaluating legal opinions of the companions, successors, and, in particular, a small group of postsuccessor jurists. I conclude by locating Ibn al-Mundhir within the literature of juristic disagreement (ikhtilāf) and highlighting the features that make his writings exceptional within this tradition.