And Jesus gave them leave. And the unclean spirits went out, and entered into the swine: and the herd ran violently down a steep place into the sea, (there were about two thousand;) and were drowned in the sea.
All Commentaries on Mark 5:13 Go To Mark 5
Tertullian of Carthage
AD 220
The devil’s legion would not have had power over the herd of swine unless they had gotten it from God. Thus they are far from having power over the sheep of God. Even the bristles of the swine were counted by God, just as were the hairs of the heads of the just. The devil, it must be admitted, seems indeed to have power—in this case really his own—over those who do not belong to God. In relation to God the idolatrous nations are all counted as a drop in the bucket, as dust on the threshing floor, as spittle in the mouth, and so thrown open to the devil as if they were a free possession. But the devil has no power over those who belong to the household of God, and cannot treat them as if they were his own. The cases marked out in Scripture show when and for what reasons he may touch the faithful. Indeed to vindicate faith, the power of trial of a believer is sometimes temporarily granted to the devil to test and challenge faith. Or to elicit repentance the sinner may be temporarily handed over to the devil as though he were an executioner to whom belonged the inflicting of punishment, as we see in the case of Saul. .