The article discusses the viewpoints of the significant missionaries of the Russian Orthodox Church on the question of necessity/ the undesirability of using of the Buryat language in learning and worship and about interconnectedness ethnic and confessional identity. Gives the opinion of the head of Transbaikalian spiritual mission, later the head of the Irkutsk diocese Benjamin (Blagonravov). Benjamin proved the need to use Russian language in teaching the Buryat and worship for them. He set the purpose of Russification the Buryats and believed that the preservation of the Buryat language will lead to the preservation of ethnic identity. Given the opposite point of view of the Kazan teacher and missionary N. I. Ilmenskiy. Used correspondence both discussants with each other and with the chief Procurator of the Synod K. P. Pobedonostsev, and letters from Benjamin to his friend, the head of the Altai spiritual mission Vladimir (Petrov).