6 Let no one therefore be high-minded on account of these matters, but let him consider the forefathers of the Lord, and put away all his haughtiness, and let good actions be his pride; or rather, not even these. For thus it was that the Pharisee came to be inferior to the Publican. Thus, if you would show the good work to be great, have no high thought, and you have proved it so much the greater. Make account that you have done nothing, and then you have done all. For if, being sinners, when we account ourselves to be what we are, we become righteous, as indeed the Publican did; how much more, when being righteous we account ourselves to be sinners. Since if out of sinners men are made righteous by a lowly mind (although this were not to be lowly-minded but to be right-minded); if then to be right-minded avails so much in the case of sinners, consider what will not lowliness of mind do with respect to righteous men.
Do not then mar your labors, nor cast away from you the fruits of your toils, neither run thou in vain, making frustrate all your labor after the many courses you have run. Nay, for your Lord knows your good works better than you do. Though thou give but a cup of cold water, not even this does He overlook; though thou contribute but a farthing, though you should utter a sigh only, He receives it all with great favor and is mindful thereof, and assigns for it great rewards.
But wherefore do you search out your own doings, and bring them out before us continually? Do you not know, that if you praise yourself, God will no more praise you? Even as if you bewail yourself, He will not cease proclaiming you before all. For it is not at all His will that your labors should be disparaged. Why do I say, disparaged? Nay, He is doing and contriving all things, so that even for little He may crown you; and He goes about seeking excuses, whereby you may be delivered from hell. For this cause, though you should work but the eleventh hour of the day, He gives your wages entire; and though thou afford no ground of salvation, He says, “I do it for my own sake, that my name be not profaned:” though you should sigh only, though you should only weep, all these things He quickly catches hold of, for an occasion of saving you.
Let us not therefore lift up ourselves, but let us declare ourselves unprofitable, that we may become profitable. For if you call yourself approved, you have become unprofitable, though thou were approved; but if useless, you have become profitable, even though thou were reprobate.
Source: Homilies on the Gospel of St. Matthew (New Advent)