Basil of Caesarea

Beasts bear witness to the faith. Hast thou confidence in the Lord? "Thou shalt walk upon the asp and the basilisk and thou shalt trample under feet the lion and the dragon." With faith thou hast the power to walk upon serpents and scorpions. Do you not see that the viper which attached itself to the hand of Paul, whilst he gathered sticks, did not injure him, because it found the saint full of faith? If you have not faith, do not fear beasts so much as your faithlessness, which renders you susceptible of all corruption.

Homilies On The Hexaemeron 9:6 ↗

Augustine of Hippo

"Thou shall go upon the asp and the basilisk; the lion and the dragon shall you tread under your feet" [Psalm 91:13]. 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. …

Exposition on Psalm 91 ↗

Jerome

The rest of what follows pertains to the same exposition. But that the just and those dear to God have the power to trample upon the ancient and twisted serpent, and to press down his whole army with the heel of the foot, we find most evidently in the Gospel. For thus the Lord says to the apostles: "Behold, I have given you power to tread upon serpents and scorpions." Which power we too shall be able to understand as given to us, when we know ourselves to be girded against them by an apostolic way of life. …

Homily 68, on Psalm 90 (Alternate Series) ↗