52 Here some one will say, This is now not to write of virginity, but of humility. As though truly it were any kind of virginity, and not that which is after God, which we had undertaken to set forth. And this good, by how much I see it to be great, by so much I fear for it, lest it be lost, the thief pride. Therefore there is none that guards the virginal good, save God Himself Who gave it: and God is Charity. The Guardian therefore of virginity is Charity: but the place of this Guardian is humility.
There forsooth He dwells, Who said, that on the lowly and quiet, and that trembles at His words, His Spirit rests. What, therefore, have I done foreign from my purpose, if wishing the good, which I have praised, to be more securely guarded, I have taken care also to prepare a place for the Guardian? For I speak with confidence, nor have I any fear lest they be angry with me, whom I admonish with care to fear for themselves together with me. More easily do follow the Lamb, although not wherever He shall have gone, yet so far as they shall have had power, married persons who are humble, than virgins who are proud.
For how does one follow Him, unto Whom one wills not to approach or how does one approach Him, unto Whom one comes not to learn, “in that I am meek and lowly of heart?” Wherefore those the Lamb leads following wherever He shall have gone, in whom first Himself shall have found where to lay His Head. For also a certain proud and crafty person had said to Him, “Lord, I will follow You wherever You shall have gone;” to whom He made answer, “Foxes have dens, and fowls of heaven nests: but the Son of Man has not where to lay His Head.”
By the term of foxes He reproved wily craftiness, and by the name of birds puffed-up arrogance, wherein He found not pious humility to rest in. And by this no where at all did he follow the Lord, who had promised that he would follow Him, not unto a certain point of progress, but altogether wherever He should have gone.
Source: On Holy Virginity (New Advent)