Therefore, when anyone receives the name of abbot he is to govern his disciples by a twofold teaching: that is, he must show forth all that is good and holy more by deeds than by words; declaring to receptive disciples the commandments of the Lord with words, but demonstrating the divine precepts to the stubborn and the simple-minded by the example of his deeds. And all of the things which he teaches his disciples are contrary (to the law of God) – it should be seen from his own actions that these are not to be done, lest while preaching to others, he himself be found reprobate (1 Cor. 9:27); and God say to him in his sin: How is it that you recite my justice and declare my covenant with your mouth, when you hate discipline and cast my words behind you (Ps. 50:16-17)? And also this: How is it that you can see a speck in your brother’s eye, and not notice the plank in your own (Matt. 7:3)?
Rule of Benedict, Chapter 2