31 Whence the greatness of this service, unto the undertaking of which we have according to our strength exhorted, the more excellent and divine it is, the more does it warn our anxiety, to say something not only concerning most glorious chastity, but also concerning safest humility. When then such as make profession of perpetual chastity, comparing themselves with married persons, shall have discovered, that, according to the Scriptures, the others are below both in work and wages, both in vow and reward, let what is written straightway come into their mind, “By how much you are great, by so much humble yourself in all things: and you shall find favor before God.” The measure of humility for each has been given from the measure of his greatness itself: unto which pride is full of danger, which lays the greater wait against persons the greater they be.
On this follows envying, as a daughter in her train; forsooth pride straightway gives birth to her, nor is she ever without such a daughter and companion. By which two evils, that is, pride and envying, is the devil (a devil). Therefore it is against pride, the mother of envying, that the whole Christian discipline chiefly wars. For this teaches humility, whereby both to gain and to keep charity; of which after that it had been said, “Charity envies not;” as though we were asking the reason, how it comes to pass that it envies not, he straightway added, “is not puffed up;” as though he should say, on this account it has not envying, in that neither has it pride.
Therefore the Teacher of humility, Christ, first “emptied Himself, taking the form of a servant, made in the likeness of men, and found in fashion as a man, He humbled Himself, made obedient even unto death, even the death of the Cross.” But His teaching itself, how carefully it suggests humility, and how earnest and instant it is in commanding this, who can easily unfold, and bring together all witnesses for proof of this matter? This let him essay to do, or do, whosoever shall wish to write a separate treatise on humility; but of this present work the end proposed is different, and it has been undertaken on a matter so great, as that it has chiefly to guard against pride.
Source: On Holy Virginity (New Advent)