Exorcism is known all over the world. Generally, if it is not a Christian exorcist, the driving out of the demon is done by bribery. You cajole and beg and bribe the spirit to leave the affected/afflicted person. Even so, we Christians believe that if a spirit isn't cast out in the name of Christ, it often is playing a trick and will only get the person in greater trouble in the future. Only when a demon is cast out in the name of Jesus and sent to the feet of Jesus for judgement is a person free from it. And even then, a person must not be left "empty" but must be filled with the knowledge of God and of His son, our Saviour Jesus Christ.
The seven sons of Sceva used the name of Jesus to cast out demons because they saw the success of using the name, but they were not Christians. In one way, their not being Christians didn't really matter. Even before Jesus died, he had given authority to his disciples to cast out demons in his name.
At that time, someone who was not part of Jesus group heard Jesus and started casting out devils. We don't know if he believed in Jesus or not. We only know he was not part of Jesus' group. But he understood one of the keys to the kingdom...the power of Jesus' name. Jesus' disciples forbade the man from casting out the devils in Jesus' name because the man was not a part of their group. Who knows why they forbade it? Perhaps they wanted to spare the man future trouble because the man was alone and we know devils can be nasty. Perhaps they wanted the man to go all the way and join them as a child and follower of Jesus. Perhaps the man thought he was some great person and liked to be known as a exorcist. Perhaps the man was setting himself up as someone who could folks a little Jesus-lite, and giving people just what they needed from God without the people having to go all the way and accept Jesus. We don't know what was happening with this guy. Although Jesus' disciples were annoyed that this fellow was doing it, Jesus told them not to forbid the man. After all, the man was doing it in Jesus name and perhaps was well on his way to believing in Jesus as the Messiah.
Later, Jesus again gives the holy spirit and the command to cast out demons after his resurrection. (He had given the spirit and the authority to them before. And he would give it to them later again at Pentecost. The Holy spirit was always being given to folks but only at Pentecost was it given without measure.)
So here we are at the Seven Sons of Sceva. It seems that there were a bunch of itinerant Jewish preachers who were going about casting out demons. We don't know how many itinerant Jewish preachers there were. The verse is mentioned before God mentions the seven sons of Chief Priest Sceva. These itinerant Jewish preachers obviously all had some success as well. Of these itinerant Jewish preachers, there were these seven sons of a Chief Priest.
These seven sons of Sceva might have exorcized people before using Jesus' name. Nowhere does it say that this famous encounter was their first rodeo. But for some reason, this particular encounter caused them trouble. Why then did this particular spirit beat them? Why then?
One of the reasons might be the kind of spirit they were attempting to exorcize. As Jesus said, some spirits don't come out that easily.
Another reason is that these were seven sons of a chief priest. Sin in the life of an exorcist or healer makes healing and exorcising hard. There is much we don't know as Christians so it's pretty stupid for us to believe that God doesn't heal or that God doesn't remove demons if the entire Christian body doesn't know all there is to know about healing. But if there is one thing that we Christians won't admit it's this: sin in the life of a healer/exorcist is not going to help. IF one gets prayed for by a minister, it might not be his lack of faith of your lack of faith. It could be the minister doesn't know what he's doing or the minister has some sin in his life. Anyway, I digress. Back to these seven sons. It is quite probable their reliance on their own holiness and importance and eliteness and legalism and family hierarchy got in the way. It is hard to exorcise a spirit when Christian exorcism is based on grace. In addition, the spirit's answer to them shows his idea of them. These Chief priest's sons are proud and legalistic. Both sins that are utterly anathema to grace. And faith and authority and power work by grace. The spirits basically puts them in their place. "I know Paul, I acknowledge Jesus. But who the heck are you?"
Can any of us Christians say we are free from pride and legalism?
11And God wrought special miracles by the hands of Paul: 12So that from his body were brought unto the sick handkerchiefs or aprons, and the diseases departed from them, and the evil spirits went out of them. 13Then certain of the vagabond Jews, exorcists, took upon them to call over them which had evil spirits the name of the Lord Jesus, saying, We adjure you by Jesus whom Paul preacheth. 14And there were seven sons of one Sceva, a Jew, and chief of the priests, which did so. 15And the evil spirit answered and said, Jesus I know, and Paul I know; but who are ye? 16And the man in whom the evil spirit was leaped on them, and overcame them, and prevailed against them, so that they fled out of that house naked and wounded. 17And this was known to all the Jews and Greeks also dwelling at Ephesus; and fear fell on them all, and the name of the Lord Jesus was magnified. 18And many that believed came, and confessed, and shewed their deeds. 19Many of them also which used curious arts brought their books together, and burned them before all men: and they counted the price of them, and found it fifty thousand pieces of silver. 20So mightily grew the word of God and prevailed.
"Master," said John, "we saw a man driving out demons in your name and we tried to stop him, because he is not one of us." Luke 9:49