20 But then in the correction and repressing of other men's sins, one must take heed, that in rebuking another he do not lift up himself; and that sentence of the Apostle must be thought of, “Wherefore let him that 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. “If a man be overtaken in a fault,” as the same Apostle says, “ye which are spiritual restore such an one in the spirit of meekness; considering yourself, lest you also be tempted. Bear ye one another's burdens, and so shall you fulfil the law of Christ.” And again in another place, “The servant of the Lord must not strive, but be gentle unto all men, apt to teach, patient, in meekness instructing those that oppose themselves; if God perhaps will give them repentance to the acknowledging of the truth; and that they may recover themselves out of the snare of the devil, who are held captive by him at his will.” So then be neither consenting to evil, so as to approve of it; nor negligent so as not to reprove it; nor proud so as to reprove it in a tone of insult.
Source: Sermons on Selected Lessons of the New Testament (New Advent)