There is a fragment of a Slavic translation of the “Letter of the Three Oriental Patriarchs to Emperor Theophilos” in a 15th-century Russian manuscript. The fragment contains the opening part of the “Letter” and considers the relations between state and church authorities. Comparison with the translation of the entire “Letter,” which is known as “Mnogoslozhnyi svitok,” proves that these translations are different. A comparison with the Greek text of the “Letter” allows us to identify the Greek manuscript closest to the Russian fragment. One can suggest that the manuscript belongs to a Russian scribe who was interested in texts related to the formation of the structure of state authority in Russia.