17 “Thou shall go upon the asp and the basilisk; the lion and the dragon shall you tread under your feet”. You know who the serpent is, and how the Church treads upon him, as she is not conquered, because she is on her guard against his cunning. And after what manner he is a lion and a dragon, I believe you know also, beloved. The lion openly rages, the dragon lies secretly in covert: the devil has each of these forces and powers. When the Martyrs were being slain, it was the raging lion: when heretics are plotting, it is the dragon creeping beneath us.
You have conquered the lion; conquer also the dragon: the lion has not crushed you, let not the dragon deceive you....A few women in the Church have bodily virginity: but the virginity of the heart all the faithful have. In the very matter of faith he feared that the heart's virginity would be corrupted by the devil: and those who have lost it, are uselessly virgins in their bodies. What does a woman who is corrupt in heart preserve in her body? Thus a Catholic married woman is before a virgin heretic. For the first is not indeed a virgin in her body, but the second has become married in her heart; and married not unto God as her husband, but unto the dragon. But what shall the Church do? The basilisk is the king of serpents, as the devil is the king of wicked spirits.
Source: The Enarrations, or Expositions, on the Psalms (New Advent)