The present article represents two significant issues of John of Dailam’s actions, Syriac Christian saint, who lived in Iran after Arab’s conquest and in the time of Umayyad Khalifa “Abd-almalik ibn marwan” in the late seventh and early eighth century A.D. one of these issues describes the relationship between Christian monks, including him, and the khalifas, governers or nobles through the healing skill in which Christians famously mastered and sometimes, some of them, like John of Dailam, implemented it by means of prophet-like miracles which were attributed to them. the other issue relates to the selection of Persian language as the monastery language in the city of Arrajān in Pars. John of Dailam apparently consented to use it in the Persian- speaking monastery, which could possibly be considered iconoclasm and non- conformity with Syriac church’s regulations concerning the language of praying. Both of these issues seem to have been related to Iranian religious, cultural and linguistic backgrounds and despite the disapproval of some bishops and their inappropriate attitudes regarding the Iranian backgrounds prior to Islam in Iran, John of Dailam took actions concerning the aforementioned issues then. With respect to the relevant studies, these two considerable issues not only led to the spread of Christianity among the Iranians of the region at that time, but also the resistance of the Persian speakers caused the Persian language to replace the non- Iranian language in the prayers of the Persian- speaking monastery. Thus, while finding or maintaining a place in Iranian Christianity, notwithstanding the decline of its official form at that juncture, the Persian language continued to exist,even in verbal form among its speakers.