They went to Capernaum, and when the Sabbath came, Jesus went into the synagogue and began to teach. The people were amazed at his teaching, because he taught them as one who had authority, not as the teachers of the law. Just then a man in their synagogue who was possessed by an evil[a] spirit cried out, "What do you want with us, Jesus of Nazareth? Have you come to destroy us? I know who you are—the Holy One of God!"Thanks BibleGateway. Checking out the Commentary on this passage, I gain the insight that unlight your typical exorcism story in the bible, Jesus does not say a special incantation, nor does he appeal to God for authority. Rather, he does the work himself. I remember a friend from grade school whose dad was a Nazarene preacher. He told me one day that the problem with the Catholics was this idea of using all these special words to exorcise deamons when really Mark told you just to tell the deamons to leave. There might be a rich area of exploration there.
"Be quiet!" said Jesus sternly. "Come out of him!" The evil spirit shook the man violently and came out of him with a shriek.
The people were all so amazed that they asked each other, "What is this? A new teaching—and with authority! He even gives orders to evil spirits and they obey him." News about him spread quickly over the whole region of Galilee.
The other academic I bring to the table in considering this scripture is Marcus Borg. In Jesus, and elsewhere, Borg suggests that the Gospels are made up of two types of stories--pure allegory and memory remembered as witness. Others would add newspaper account or history, but I agree with Borg that nothing in the Gospels was written that way. Because of the language about deamons talking and whatnot, it is easy to put this in the pure allegory folder. But, I'm slow to do that. Mark is such a no nonesense Gospel, and the author talks about healing a lot. Was Jesus skilled at helping the insane? Consider Annie Sullivan. Could he have had a way about him that brought an end to the suffering of troubled people? And then, in writing the story of his life, Mark would include that as evidence of his greatness? That I think is the best reading of this story.