Acts 19:13 – 17
New International Version (NIV)
13 Some Jews who went around driving out evil spirits tried to invoke the name of the Lord Jesus over those who were demon-possessed. They would say, “In the name of the Jesus whom Paul preaches, I command you to come out.” 14 Seven sons of Sceva, a Jewish chief priest, were doing this. 15 One day the evil spirit answered them, “Jesus I know, and Paul I know about, but who are you?” 16 Then the man who had the evil spirit jumped on them and overpowered them all. He gave them such a beating that they ran out of the house naked and bleeding.
17 When this became known to the Jews and Greeks living in Ephesus, they were all seized with fear, and the name of the Lord Jesus was held in high honor.
From BibleGateway.com: http://www.biblegateway.com/passage/?search=Acts+19.13-17&version=NIV