Matthew Henry Commentary Mark 1:23-28

"And straightway there was in their synagogue a man with an unclean spirit; and he cried out, saying, What have we to do with thee, Jesus thou Nazarene? art thou come to destroy us? I know thee who thou art, the Holy One of God. And Jesus rebuked him, saying, Hold thy peace, and come out of him. And the unclean spirit, tearing him and crying with a loud voice, came out of him. And they were all amazed, insomuch that they questioned among themselves, saying, What is this? a new teaching! with authority he commandeth even the unclean spirits, and they obey him. And the report of him went out straightway everywhere into all the region of Galilee round about." — Mark 1:23-28 (ASV)

The devil is an unclean spirit because he has lost all the purity of his nature, because he acts in direct opposition to the Holy Spirit of God, and by his suggestions defiles the spirits of people. There are many in our assemblies who quietly attend under merely formal teachers; but if the Lord comes with faithful ministers and holy doctrine, and by his convincing Spirit, they are ready to say, like this man, What have we to do with you, Jesus of Nazareth! No disorder could enable a person to know Jesus to be the Holy One of God.

He desires to have nothing to do with Jesus, for he despairs of being saved by him, and dreads being destroyed by him. See whose language those speak who say to the Almighty, Depart from us. This unclean spirit hated and dreaded Christ, because he knew him to be a Holy One; for the carnal mind is enmity against God, especially against his holiness. When Christ by his grace delivers souls out of the hands of Satan, it is not without tumult in the soul, for that spiteful enemy will disquiet those whom he cannot destroy.

This led all who saw it to consider, What is this new doctrine? A work as great is often done now, yet people treat it with contempt and neglect. If this were not so, the conversion of a notorious, wicked person to a sober, righteous, and godly life, by the preaching of a crucified Saviour, would cause many to ask, What doctrine is this?