I know who you are - the Holy One of God

Luke 4:31-44
In Capernaum, Jesus drives out an evil spirit. I know who you are - the Holy One of God. The demon cried out.
All the people were amazed and said to each, 'What is this teaching? With authority and power he gives orders to evil spirits and they come out.
The people were looking for Jesus and keep him from leaving them. But he said, "I must preach the good news of the kingdom of God to the other towns also, because that is why I was sent."
Luke picks up Mark's narrative at this point, but by placing the two synagogue/sabbath stories next to one another brings out the sharp contrast in people's response to Jesus. He also adds personal touches. The 'high fever' of verse 38 is a medical term, and he tells us that Jesus laid his hands on those he cured.
Demon: In the ancient world it was widely held that many troubles are caused by evil spirit The bible says little about demon possession before or after the incarnation, but much during Jesus ministry...: this phenomenon is part of the conflict between Jesus, who came to destroy the works of the devil, and evil.
Why?
It is contrast in people's response to Jesus between two towns.
People amazed at Jesus works but with difference response.
Even the demon know who Jesus is - the Holy One of God.
Jesus works with authority and power over demon and fever. Jesus can cure the sicks.
Demon accept Jesus but they did not be saved, so it is not rational understanding, but spiritual turn from sins and accept Jesus as our Lord.
How?
Accept Jesus Christ as my Lord and confess out sins and turn to Jesus Christ.