Luke 10:19

“Behold, I have given you authority to tread on serpents and scorpions, and over all the power of the enemy, and nothing will in any way hurt you.”

The result of Satan's fall, whether seen as actually having happened or as potential, is that those who are in the Kingly Rule of God have authority over all his minions who can be trodden underfoot, for Jesus has given His ambassadors authority over them. And this is what they have been engaged in. There is here a glance towards Genesis 3:15 where the curse on the Serpent was to result in the bruising of his head by man as he himself struck at man's heel. This bruising was now in process (and would continue - Romans 16:20). The evil spirits which are symbolised as serpents and scorpions can do no harm to those sheltered under the authority of Jesus who can tread on them with impunity. Even their heels are not vulnerable. They will find this guaranteed by the fact that physical serpents and scorpions will be unable to hurt them as well (compare Mark 16:18), but this last is secondary, it is but a symbol of the real thing. For the idea of treading on serpents compare Psalms 91:13. Because they are within God's Kingly Rule serpents have become their plaything (Isaiah 11:8).

‘The power (dunamis) of the Enemy.' That is, the power of Satan and all the forces of evil. Though they may have to battle with him (Ephesians 6:12) those who are truly in Christ need fear nothing of him, for Christ is with them. While Satan has may have a certain ‘power' (dunamis) Jesus has total authority over him (exousia), and He has given it to His own.