Summary point
Importance to have the right authority from God to cast out demons vs 15 or to perform healing vs 11.
Acts 19:11-16
[11]God was performing unusual miracles through Paul.
[12]Even handkerchiefs and aprons he had used were taken to those who were ill, and their diseases were driven away, and the evil spirits would go out of them.
[13]Some Jews who travelled round and drove out evil spirits also tried to use the name of the Lord Jesus to do this. They said to the evil spirits, “I command you in the name of Jesus, whom Paul preaches.”
[14]Seven brothers, who were the sons of a Jewish High Priest named Sceva, were doing this.
[15]But the evil spirit said to them, “I know Jesus, and I know about Paul; but you — who are you?”
[16]The man who had the evil spirit in him attacked them with such violence that he overpowered them all. They ran away from his house, wounded and with their clothes torn off.