9 Wherefore our care of our conduct has need to be great. Why, this is the very reason of our continually assembling you here; not simply that you should enter in, but that you should also reap some fruit from your continuance here. But if you come indeed constantly, but go away again reaping no fruit from thence, you will have no advantage from your entering in and attendance in this place.
For if we, when sending children to teachers, should we see them reaping no benefit thereby, begin to be severe in blaming the teachers, and remove them often to others; what excuse shall we have for not bestowing upon virtue even so much diligence as upon these earthly things, but forever bringing our tablets home empty? And yet our teachers here are more in number and greater. For no less than prophets and apostles and patriarchs, and all righteous men, are by us set over you as teachers in every Church. And not even so is there any profit, but if you have joined in chanting two or three Psalms, and making the accustomed prayers at random and anyhow, are so dismissed, you think this enough for your salvation. Have ye not heard the prophet, saying (or rather God by the prophet), “This people honors me with their lips, but their heart is far from me?”
Therefore, lest this be our case too, wipe out the letters, or rather the impressions, which the devil has engraven in your soul; and bring me a heart set free from worldly tumults, that without fear I may write on it what I will. Since now at least there is nothing else to discern, except his letters—rapines, covetings, envy, jealousy. Wherefore of course, when I receive your tablets, I am not able so much as to read them. For I find not the letters, which we every Lord's day inscribe on you, and so let you go; but others, instead of these, unintelligible and misshapen. Then, when we have blotted them out, and have written those which are of the Spirit, you departing, and giving up your hearts to the works of the devil, give him again power to substitute his own characters in you. What then will be the end of all this, even without any words of mine, each man's own conscience knows. For I indeed will not cease to do my part, and to write in you the right letters. But if you mar our diligence, for our part our reward is unaltered, but your danger is not small.
Now, though I would fain say nothing to disgust you, yet I beseech again and entreat you, imitate at least the little children's diligence in these matters. For so they first learn the form of the letters, after that they practise themselves in distinguishing them put out of shape, and then at last in their reading they proceed orderly by means of them. Just so let us also do; let us divide virtue, and learn first not to swear, nor to forswear ourselves, nor to speak evil; then proceeding to another row, not to envy, not to lust, not to be gluttonous, not to be drunken, not fierce, not slothful, so that from these we may pass on again to the things of the Spirit, and practise continence, and neglect of the belly, temperance, righteousness, to be above glory, and gentle and contrite in mind; and let us join these one with another, and write them upon our soul.
Source: Homilies on the Gospel of St. Matthew (New Advent)