St. Mark (1:21–28) and St. Luke (4:31–37) place this as the first public exorcism of Our Lord's ministry, in the synagogue at Capernaum (whose ruins are still visible at Tell Hum on the north shore of the Sea of Galilee). Christ had just begun to teach 'as one having power, and not as the scribes' when a man with an unclean spirit cried out: 'What have we to do with thee, Jesus of Nazareth? art thou come to destroy us? I know who thou art, the Holy One of God.'
The Lord commanded the spirit: 'Speak no more, and go out of the man.' The spirit, tearing the man and crying out with a loud voice, came out of him. 'And they were all amazed, insomuch that they questioned among themselves, saying: What thing is this? what is this new doctrine? for with power he commandeth even the unclean spirits, and they obey him.' The miracle spread the Lord's reputation throughout all Galilee.
The Fathers note that the demons knew Christ — confessed Him as 'the Holy One of God' — better than the human authorities who would later condemn Him. The exorcism is the first overt collision in the Gospels between the Kingdom of God and the kingdom of darkness.