9 Wherefore neither are we to believe that their fruitfulness of the flesh, who at this time seek in marriage nothing else save children, to make over unto Christ, can be set against the loss of virginity. Forsooth, in former times, unto Christ about to come after the flesh, the race itself of the flesh was needful, in a certain large and prophetic nation: but now, when from out every race of men, and from out all nations, members of Christ may be gathered unto the People of God, and City of the kingdom of heaven, whoso can receive sacred virginity, let him receive it; and let her only, who contains not, be married. For what, if any rich woman were to expend much money on this good work, and to buy, from out different nations, slaves to make Christians, will she not provide for the giving birth to members of Christ in a manner more rich, and more numerous, than by any, how great soever, fruitfulness of the womb?
And yet she will not therefore dare to compare her money to the offering of holy virginity. But if for the sake of making such as shall be born Christians, fruitfulness of the flesh shall with just reason be set against the loss of chastity, this matter will be more fruitful, if virginity be lost at a great price of money, whereby many more children may be purchased to be made Christians, than could be born from the womb, however fruitful, of a single person. But, if it be extreme folly to say this, let the faithful women that are married possess their own good, of which we have treated, so far as seemed fit, in another volume; and let them more highly honor, even as they are most rightly used to do, in the sacred virgins, their better good, of which we are treating in our present discourse.
Source: On Holy Virginity (New Advent)