Luke 9:49-50 (ESV)
John answered, "Master, we saw someone casting out demons in your name, and we tried to stop him, because he does not follow with us."  But Jesus said to him, "Do not stop him, for the one who is not against you is for you."
We tried to stop him because he does not follow us. The first thing that comes to my mind after reading this is the Seven Sons of Sceva in Acts 19. They tried to cast out demons in the name of Jesus while not believing in Jesus, and the demons beat the tar out of them.
I am not one who discounts demons. I believe in angels, and so I have to believe in demons. A couple angels saved my life the other day. And when four people I don’t know show up on a scene declaring to be EMTs within five minutes of a rollover, when it takes the ambulance more than a half an hour to get there, (understandable considering where we were) and the UHP at least 45 minutes, then I think I possible shook hands with a couple. Yet, it is all conjecture. I believe they are there because Christ tells me they are. I have no tangible proof. But if I get to heaven and find out the girl with the foxy t-shirt on and the tramp stamp, who made Bryan and I sit while she examined us for concussions, was an angel, I doubt I’ll bat an eye. She was awesome. Same with the truck driver David Wilkerson, I can’t remember all the people. But I do, I do believe there were angels there.
So I also believe in demons. And I believe in exorcisms. Baptism is actually an exorcism. In Jesus day there were many exorcists. Even as there are still today in many third world countries, and dismissing what they do is not as easy as it perhaps looks. My friend Robert Bennet just published an excellent book on exorcism in Madagascar and Haiti. The Lutheran population of Madagascar has exploded due to successful exorcisms on behalf of a lay movement of exorcists. You go tell the people that have been healed that the exorcists are crazy, I’m not going to.
This man was casting out demons in Jesus name, but he did not follow Jesus. More or less this means he wasn’t a disciple. But Jesus says the one who is not against you is for you. The man obviously had some faith in the name of Jesus, otherwise he would not be using it. Perhaps he had reason not to be “following Jesus” how the disciples would know he wasn’t a disciple is a bit perplexing. But the man wasn’t in the 12, or following Jesus around with the rest of the entourage either. Jesus knows though that this man’s work is a testimony to him. On the other hand, the Sons of Sceva had actively rejected Jesus, and yet still wanted to use his name. The demons set them straight. I think the story is told because the Sons of Sceva realized they better start believing. The demons recognized Paul and Jesus, but had no sympathy for the posers.