Mark 9:38-40 and Luke 9:49-50 both record a strange moment during the ministry of Jesus. In each passage John explains the disciples had seen someone casting out demons in Jesus’ name, by His authority, and they attempted to stop him because he was not walking with them. Jesus then gave a corrective response, instructing them to leave him alone. Jesus reasoned that after performing a miracle in His name the man would not be able to quickly speak evil of Him. Jesus then gave a principle to live by: “For he who is not against us is for us.”
The motivation of the disciples was filled with ego and pride: because this man was not in their group, they tried to stop him from doing things that were right and good (casting out demons) in the name of Jesus.
Jesus’ response becomes very reasonable when paired with the correct understanding of the purpose of miracles. Miracles are designed to prove a message, or to confirm a thing or person as having been sent by the authority of God (Mark 16:20). Jesus understands this man, because He is performing true miracles by the authority of Jesus Himself, will not be allowed by God to speak what is false. If he performed a miracle and then spoke what was false, then the lie he taught would have been lent God’s authority and confirmation, which will never be the case (Numbers 23:8). Jesus understood that truth, and it prompted His comforting, corrective response. They didn’t need to worry about it, because this man would only be able to speak the truth after performing a miracle in the name of Jesus.
Christians today can get caught up in rivalries that damage the effectiveness of the gospel. The statement of Jesus, “For he who is not against us is with us,” means, in modern circumstances, “If a person is doing and teaching what God calls right, he is our ally”.
This is not a statement designed to teach tolerance of false doctrine or practice. The Scriptures teach just the opposite many times (Galatians 1:6-8). When the context is allowed to interpret these statements of Jesus, we learn about miracles and how the power of God directed the individuals through whom it worked, and we are reminded to remain humble by cooperating with those who do and teach the Bible as God intended.