Drawing upon materials from the State Archive of the Orenburg Region, the article reconstructs the biography, religious views and practices of the peasant Pyotr Maklakov, who “dropped out of Orthodoxy into the Sabbaterian sect” and actively propagated “the Jewish faith” among the inhabitants of the Orenburg district in the late 19th — early 20th centuries. Particular attention is paid to the reasons for such “deviation” (conversion) to Judaizers, the methods of spreading Judaism among the peasants, discussions between the followers of the Sabbaterian sect and Christian Orthodoxy, the circumstances of bringing the sectarian to legal responsibility. The author traces the evolution of religious practices of Pyotr Maklakov and his inner circle. Since he was twice prosecuted by secular and ecclesiastical authorities with an interval of ten years, the archival documents reflect the gradual transition of the sectarian from a “Jewish faith,” spontaneously reconstructed from Christian sources, to Orthodox Judaism with its normative practices and prayer in Hebrew according to Siddur. The author also shows a contradictory combination of normative Jewish practices with active missionary activity unusual for rabbinical Judaism.