2 Cease then to urge us on to a penalty so inevitable; for our discourse is not about an army, or a kingdom; but about an office which needs the virtues of an angel. For the soul of the Priest ought to be purer than the very sunbeams, in order that the Holy Spirit may not leave him desolate, in order that he may be able to say, “Now I live; and yet no longer I, but Christ lives in me.” For if they who dwell in the desert, and are removed far from the city and the market-place, and the tumult therein, and who enjoy all their time a haven of rest, and of peacefulness, are not willing to rely on the security of that manner of life, but add to it numberless other safeguards, hedging themselves round on every side, and studying both to speak and to act with great circumspection, so that to the utmost extent of human power they may draw near to God with assurance, and with unstained purity, what power and strength, do you think, does the ordained Priest need so as to be able to tear his soul away from every defilement, and to keep its spiritual beauty unsullied?
For he has need of far greater purity than they; and whoever has need of greater purity, he too is subject to more pressing temptations than they, which are able to defile him, unless by using constant self-denial and much labor, he renders his soul inaccessible to them. For beauty of face, elegance of movement, an affected gait and lisping voice, pencilled eyebrows and enamelled cheeks, elaborate braiding and dyeing of hair, costliness of dress, variety of golden ornaments, and the glory of precious stones, the scent of perfumes, and all those other matters to which womankind devote themselves, are enough to disorder the mind, unless it happen to be hardened against them, through much austerity of self restraint.
Now to be disturbed indeed by such things is nothing wonderful. But on the other hand, that the devil should be able to hit and shoot down the souls of men by the opposite of these— this is a matter which fills us with astonishment and perplexity.
Source: On the Priesthood (New Advent)