This article focuses on a passage from letter I.6 of Pope Gregory I the Great addressed to the Byzantine noble Narses, with whom the Pope became closely acquainted in Constantinople. Gregory rebukes his addressee for trying to “plow the field of the Lord” with the help of oxen (bubali), which are unsuitable for this matter. Gregory also advises Narses to “smite them with the sword of his mouth”. In order to unravel the meaning of Gregory’s metaphor we analyze the context of his letter (including references to the Bible), as well as all his messages to Narses. Four extant letters touch on theological and church matters, so Narses could be close to the circle of patriarch John IV. His help to Gregory in the case of accused eastern presbyters or with Church Councils’ manuscripts could be metaphorically designated as “plowing the field of the Lord”. Letter I.6 by Gregory probably points to some theological or church dispute that took place in the patriarchal or imperial court. Bubali in biblical context are oxen unfit for plowing, because they are too ferocious. In view of the conflict between Gregory I and John of Contantinople bubali may designate any persons from the patriarch’s circle. The content of the letters shows how vividly Gregory was interested in the affairs of the Church of Constantinople and in Greek theology. The context of the messages allows us to make an assumption about what the Pope had in mind when speaking of bubali.