5 I know that you are Godfearing, merciful, gentle, and calm, having the faith and fear of God at heart, but often some things escape our notice. “Some have a zeal of God, but not according to knowledge.” And I think that we ought to take care lest this also come upon faithful souls. I know your piety towards God, your lenity towards men, I myself am bound by the benefits of your favour. And therefore I fear the more, I am the more anxious; lest even you condemn me hereafter by your own judgment, because through my want of openness or my flattery you should not have avoided some fault. If I saw that you sinned against me, I ought not to keep silence, for it is written: “If your brother sin against you, rebuke him at first, then chide him sharply before two or three witnesses. If he will not hear you, tell the Church.” Shall I, then, keep silence in the cause of God? Let us, then, consider what I have to fear.
Source: Letters (New Advent)