This dissertation is a literary and historical study of the relationship between canonization of texts and religious community formation. A story that is not represented in accounts of Muslim history, this project examines how the modern day Ismaili community has come to be identified as a Shia sect of Islam. Analyzing the Aga Khan Case of 1866, I show how a caste group of khojas was given an "Ismaili" religious identity by the court. Crucial to this re-evaluation was the judge's reading of Dasavatar (Ten Avatars of Vishnu), a medieval Gujarati poem of the ginan genre, and the pronouncement that the Aga Khan was imam of this Muslim "sect." I demonstrate how the judge's declaration of the Dasavatar ginan as a conversion text -- in which Hindus became Muslims -- fundamentally transformed the self-conception of this community in the colonial and post-colonial periods. Furthermore, the logic of this conversion story persists in Ismaili studies scholarship, whereby ginan poetry is situated as part of a longer and primarily Persian Islamic narrative about conversion. As a response to this kind of sectarian interpretation of ginans as conversion literature, the dissertation, secondly, engages in readings of Dasavatar and ginan poetry as vernacular expressions and conduits of the khoja community's heterogeneous religious history. Third, the dissertation offers an instructive comparison with the ways in which the Vaishnava Swami Narayan sampradaya emerged as a sectarian religious community with its own canon in nineteenth century India -- influenced, in part, by the ginan poetic tradition. Through both textual and historical study, I explore how the formation of the Swami Narayan sect was enacted from circumstances similar to those that led to Ismaili community formation: the colonial state's official endorsement of the sect's charismatic leader and, in quite a different mode, the canonization of vernacular ginan poetry.