Luke 10:19

(Orat. in Pass. et cruce Domini.) But now through the power of Christ boys make a mock at pleasure, which formerly led away the aged, and virgins stedfastly trample upon the desires of serpentine pleasure. Some also tread upon the very sting of the scorpion, that is, of the devil, namely death, and fearing not destruction, become witnesses of the word. But many giving up earthly things walk with a free step in heaven, dreading not the prince of the air.

Serpents indeed at one time under a figure were made to bite the Jews, and kill them because of their unbelief. But there came One who should destroy those serpents; even the Brazen Serpent, (Numb. 21:8.) the Crucified, so that if any one should look on Him believing, he might be healed from his wounds and saved.

(Hom. in Cant.) For pleasure is called in Scripture a serpent, which by nature is such that if its head has reached a wall so as to press upon it, it drags its whole body after it. So nature has given man the habitation which was necessary for him. But by means of this necessity, pleasure assaults the heart, and perverts it to the indulgence of immoderate ornament; in addition to this it brings in its train covetousness, which is followed by lust, that is, the last member or tail of the beast. But as it is not possible to draw back the serpent by its tail, so to remove pleasure we must not begin with the last, unless one has closed the first entrance to evil.

Then lest we should suppose this was spoken of beasts, He added, And over all the power of the enemy.

That is, I give you the power of casting out every kind of unclean spirit, from the bodies possessed. And as far as regards themselves, He adds, And nothing shall hurt you. Although it might also be taken literally. For Paul when attacked by a viper suffered no injury. (Acts 28:5.) John having drunk poison is not harmed by ita. But I think there is this difference between serpents who bite with the teeth, and scorpions who sting with the tail, that the serpents signify men or spirits raging openly, scorpions signify them plotting in secret. Or serpents are those which east the poison of evil persuasion upon virtues just beginning, scorpions which go about to corrupt at last virtues which have been brought to perfection.