A.T. Robertson Commentary Mark 9:25

"And when Jesus saw that a multitude came running together, he rebuked the unclean spirit, saying unto him, Thou dumb and deaf spirit, I command thee, come out of him, and enter no more into him." — Mark 9:25 (ASV)

A multitude came running together (επισυντρεχε οχλος). A double compound here alone in the N.T. and not in the old Greek writers. Επιτρεχω occurs in the papyri, but not επισυντρεχω. The double compound vividly describes the rapid gathering of the crowd to Jesus and the epileptic boy to see the outcome.

Come out of him (εξελθε εξ αυτου). Jesus addresses the demon as a separate being from the boy as he often does. This makes it difficult to believe that Jesus was merely indulging popular belief in a superstition. He evidently regards the demon as the cause in this case of the boy's misfortune.