Augustine of Hippo

But then in the correction and repression of other men's sins, one must take heed that in rebuking another he does not lift up himself. The sentence of the apostle must be remembered: "Let one who thinks he stands, take heed lest he fall." Let the voice of chiding sound outwardly in tones of terror, let the spirit of love and gentleness be maintained within.… So then you must neither consent to evil, so as to approve of it, nor be negligent, so as not to reprove it, nor be proud, so as to reprove it in a tone of insult.