During the past century of oriental studies, the question of when and where Muslim traditions came to be propped up with validating lines of transmission has attracted a considerable amount of scholarly attention, for its bearing on the key issue of the historicity of ḥadīth. In this essay, I review the existing theories about the origin of the isnād, which alternate between the lifetime of the Prophet’s Companions and the end of the second century AH/c. 816 CE. Based on a (...) hitherto largely overlooked tradition and two general methodological premises, I associate the inception of corroborative attribution to past authorities in legal and theological ḥadīth with the aftermath of al-Mukhtār b. Abī ʿUbayd al-Thaqafī’s revolt in Kūfa. Over the course of the second/eighth century, the isnād institution spread out across the major centers of learning in the caliphate and entered the field of historical reports. Such geographical and typological unevenness of the isnād’s evolution gave rise to conflicting theories about its chronology. (shrink)