“Therefore, when anyone receives the name of abbot, he ought to govern his disciples with a twofold teaching.
That is to say, [1] he should show them all that is good and holy by his deeds even more than by his words, expounding the Lord’s commandments in words to the intelligent among his disciples, but demonstrating the divine precepts by his actions to those of harder hearts and ruder minds.
And [2] whatever he has taught his disciples to be contrary to God’s law, let him indicate by example that it is not to be done, lest, while preaching to others, he himself be found reprobate, and lest God one day say to him in his sin, “Why do you declare my statutes and profess my covenant with your lips, whereas you hate discipline and have cast my words behind you?” [Psalm 50:16-17] And again, “You were looking at the speck in your brother’s eye and you did not see the beam in your own. [Luke 6:41-42]”
Benedict of Nursia (c. 480-543), Rule of St. Benedict 2.