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
John Chrysostom
AD 407
He did this so that you might know that the demons would have done the same thing to human beings and would have drowned them if God had allowed them to do so. But he restrained the demons, stopped them, and allowed them to do no such thing. When their power was transferred to the swine, it became clear to all witnesses what they would have done to persons. From this we learn that if the demons had the power to possess swine, they also could have possessed humans.