30 The right question plainly is, not whether a virgin every way disobedient is to be compared to an obedient married woman, but a less obedient to a more obedient: forasmuch as that also of marriage is chastity, and therefore a good, but less than virginal. Therefore if the one, by so much less in the good of obedience, as she is greater in the good of chastity, be compared with the other, which of them is to be preferred that person judges, who in the first place comparing chastity itself and obedience, sees that obedience is in a certain way the mother of all virtues.
And therefore, for this reason, there may be obedience without virginity, because virginity is of counsel, not of precept. But I call that obedience, whereby precepts are complied with. And, therefore, there may be obedience to precepts without virginity, but not without chastity. For it pertains unto chastity, not to commit fornication, not to commit adultery, to be defiled by no unlawful intercourse: and whoso observe not these, do contrary to the precepts of God, and on this account are banished from the virtue of obedience.
But there may be virginity without obedience, on this account, because it is possible for a woman, having received the counsel of virginity, and having guarded virginity, to slight precepts: even as we have known many sacred virgins, talkative, curious, drunken, litigious, covetous, proud: all which are contrary to precepts, and slay one, even as Eve herself, by the crime of disobedience. Wherefore not only is the obedient to be preferred to the disobedient, but a more obedient married woman to a less obedient virgin.
Source: On the Good of Marriage (New Advent)