St. Ambrose explains that he is not speaking against marriage, and proceeds to compare the advantages and disadvantages of the single and married state.
24. I am not indeed discouraging marriage, but am enlarging upon the benefits of virginity. “He who is weak,” says the Apostle, “eats herbs.” I consider one thing necessary, I admire another. “Are you bound to a wife? Seek not to be loosed. Are you free from a wife? Seek not a wife.” This is the command to those who are. But what does he say concerning virgins? “He who gives his virgin in marriage does well, and he who gives her not does better.” The one sins not if she marries, the other, if she marries not, it is for eternity. In the former is the remedy for weakness, in the latter the glory of chastity. The former is not reproved, the latter is praised.
25. Let us compare, if it pleases you, the advantages of married women with that which awaits virgins. Though the noble woman boasts of her abundant offspring, yet the more she bears the more she endures. Let her count up the comforts of her children, but let her likewise count up the troubles. She marries and weeps. How many vows does she make with tears. She conceives, and her fruitfulness brings her trouble before offspring. She brings forth and is ill. How sweet a pledge which begins with danger and ends in danger, which will cause pain before pleasure! It is purchased by perils, and is not possessed at her own will.
26. Why speak of the troubles of nursing, training, and marrying? These are the miseries of those who are fortunate. A mother has heirs, but it increases her sorrows. For we must not speak of adversity, lest the minds of the holiest parents tremble. Consider, my sister, how hard it must be to bear what one must not speak of. And this is in this present age. But the days shall come when they shall say: “Blessed are the barren, and the wombs that never bare.” For the daughters of this age are conceived, and conceive; but the daughter of the kingdom refrains from wedded pleasure, and the pleasure of the flesh, that she may be holy in body and in spirit.
27. Why should I further speak of the painful ministrations and services due to their husbands from wives, to whom before slaves God gave the command to serve? And I mention these things that they may comply more willingly, whose reward, if approved, is love; if not approved, punishment for the fault.
28. And in this position spring up those incentives to vice, in that they paint their faces with various colours, fearing not to please their husbands; and from staining their faces, come to think of staining their chastity. What madness is here, to change the fashion of nature and seek a painting, and while fearing a husband's judgment to give up their own. For she is the first to speak against herself who wishes to change that which is natural to her. So, while studying to please others, she displeases herself. What truer witness to your unsightliness do we require, O woman, than yourself who art afraid to be seen? If you are beautiful, why hidest you yourself? If unsightly, why do you falsely pretend to beauty, so as to have neither the satisfaction of your own conscience, nor of the error of another? For he loves another, you desire to please another. And are you angry if he love another, who is taught to do so in your own person? You are an evil teacher of your own injury.
29. And next, what expense is necessary that even a beautiful wife may not fail to please? Costly necklaces on the one hand hang on her neck, on the other a robe woven with gold is dragged along the ground. Is this display purchased, or is it a real possession? And what varied enticements of perfumes are made use of! The ears are weighed down with gems, a different colour from nature is dropped into the eyes. What is there left which is her own, when so much is changed? The married woman loves her own perceptions, and does she think that this is to live?
30. But you, O happy virgins, who know not such torments, rather than ornaments, whose holy modesty, beaming in your bashful cheeks, and sweet chastity are a beauty, you do not, intent upon the eyes of men, consider as merits what is gained by the errors of others. You, too, have indeed your own beauty, furnished by the comeliness of virtue, not of the body, to which age puts not an end, which death cannot take away, nor any sickness injure. Let God alone be sought as the judge of loveliness, Who loves even in less beautiful bodies the more beautiful souls. You know nothing of the burden and pain of childbearing, but more are the offspring of a pious soul, which esteems all as its children, which is rich in successors, barren of all bereavements, which knows no deaths, but has many heirs.
31. So the holy Church, ignorant of wedlock, but fertile in bearing, is in chastity a virgin, yet a mother in offspring. She, a virgin, bears us her children, not by a human father, but by the Spirit. She bears us not with pain, but with the rejoicings of the angels. She, a virgin, feeds us, not with the milk of the body, but with that of the Apostle, wherewith he fed the tender age of the people who were still children. For what bride has more children than holy Church, who is a virgin in her sacraments and a mother to her people, whose fertility even holy Scripture attests, saying, “For many more are the children of the desolate than of her that has an husband”? She has not an husband, but she has a Bridegroom, inasmuch as she, whether as the Church among nations, or as the soul in individuals, without any loss of modesty, she weds the Word of God as her eternal Spouse, free from all injury, full of reason.
Source: Concerning Virgins (New Advent)