"Now God worked unusual miracles by the hands of Paul, so that even handkerchiefs or aprons were brought from his body to the sick, and the diseases left them and the evil spirits went out of them. Then some of the itinerant Jewish exorcists took it upon themselves to call the name of the Lord Jesus over those who had evil spirits, saying, 'We exorcise you by the Jesus whom Paul preaches.' Also there were seven sons of Sceva, a Jewish chief priest, who did so. And the evil spirit answered and said, 'Jesus I know, and Paul I know; but who are you?' Then the man in whom the evil spirit was leaped on them, overpowered them, and prevailed against them, so that they fled out of the house naked and wounded. This became known both to all Jews and Greeks dwelling in Ephesus; and fear fell on them all, and the name of the Lord Jesus was magnified. And many who had believed came confessing and telling their deeds. Also, many of those who had practiced magic brought their books together and burned them in the sight of all. And they counted up the value of them, and it totaled fifty thousand pieces of silver. So the word of the Lord grew mightily and prevailed" (Acts 19:11-20).
Here Luke makes record of some of the unique miracles worked through Paul. Unquestionably, God was with Paul and blessed him with amazing power. This power complemented the gospel message Paul preached, validating his ministry and proving his words to be from God (cf. Mark 16:20). The power given to him by God was so strong that even cloth taken from Paul to the sick, diseased, or demon possessed was sufficient to heal them of their affliction. This great power was noticed and desired by others, for it was far superior to the "magic" in that region which was so prevalent. Luke specifically mentions a group of traveling Jews who attempted (perhaps successfully) to cast out demons by stating - "We exorcise you by the Jesus whom Paul preaches." If they were successful, it only underscores the power of Jesus' name. Some demons may have respected the name of Jesus regardless of who invoked it. But, this was not the case with all evil spirits!
Luke reports one case where an exorcism was attempted by seven sons of Sceva, a Jewish chief priest. While attempting to cast out a demon by "the Jesus whom Paul preaches", the evil spirit engaged them with a question - "Jesus I know, and Paul I know; but who are you?" In other words, "Who do you imposters think you are?!" Although these seven men knew some powerful names (like Jesus and Paul), they went beyond their proper place in trying to exorcise demons without God's authority, and it backfired on them on this occasion. The evil spirit did not leave his host, but stirred up the man to attack these seven men with such violent force that the seven men could do nothing but flee. The demon-possessed man overpowered them, tearing their garments off them as he attempted to rip them limb from limb! Seven ordinary men were no match for one demon, but not even several thousand demons are equal to divine power (cf. Mark 5:8ff). Typically, inspired literature records men casting out demons, but here we have a demon casting out men!
This incident soon became well known in Ephesus, among all peoples. It generated great respect for the Lord and, it would seem, many converts to the cause of Christ. The name of Jesus was revered and rightly perceived to be more than some verbal charm. The great miracles worked by Paul coupled with the botched exorcism of Sceva's sons so affected the consciences of many Christians that they came and confessed their sins (probably sins pertaining to the occult), turning from them. There would have been no need to confess sins committed prior to becoming Christians, since one does not confess what is already forgiven. Thus, this must refer to sins they were involved with even after obeying the gospel. This is not surprising since it sometimes takes Christians a while to fully break free from their sordid pasts. Furthermore, some voluntarily gathered together intent on destroying their books about the occult and its wicked practices they had previously engaged in. Although the value of the books burned was great (about 50,000 pieces of silver), this did not deter them from doing what was right. They did not get rid of the books by reselling them. It would not have been appropriate to sell the illicit material in order to minimize personal loss. Destroying the books was the correct course of action; repentance is not cheap! These events helped God's word continue spreading and having great influence. Even today the word of God has great power to prevail if we live it and preach it faithfully.