De bono pudicitiae c. 1—3.

...I think I have brought forth sufficiently broad and rich praises of chastity: but I deemed it superfluous to praise it any longer among those who cherish it. For you adorn it while you practice it, and you bring forth more of its praises by exercising it, having become its ornament, just as it is yours, to be mutually returned in common grace. It suggests to you the discipline of good morals; you provide it the ministry of holy works. For both what it can do and how much it can do has appeared through you, and it itself has demonstrated and taught what you wish, with the two goods of the commandments and of deeds coupled into one, lest anything should appear mutilated if either the precepts lacked the ministries or the ministries lacked the precepts.

Chastity is the honor of bodies, the ornament of morals, the holiness of the sexes, the bond of marriages, the faith of the lineage, the bulwark of modesty, the fountain of purity, the peace of the home, the head of concord. Chastity is solicitous lest it please anyone except itself: chastity is always modest, while it is the mother of innocence: chastity is always adorned only by modesty, well conscious of its own beauty if it displeases the wicked. Chastity seeks no ornaments; it is its own beauty. It commends us to the Lord, it connects us to Christ: it conquers all unlawful battles of desires from the members, it brings peace to our bodies, being blessed itself and making blessed those among whom it deigns to dwell, which those who do not possess it can never accuse: it is venerable even to its enemies, while they admire it all the more, those who cannot conquer it. But just as this virtue is always approved in men and to be sought by women, so its enemy, unchastity, is always to be detested...