I was wondering what Jesus meant in Mark 9:38-40 where John told Him of a man who was casting out devils in Jesus' name but forbade the man from doing so because he didn't follow with them. How does the verse "For he that is not against us is on our part" apply today? I know that many people claim and preach Christ, but also preach false doctrines, though they do many works in His name. What does "for there is no man which shall do a miracle in my name, that can lightly speak evil of me" mean? Does that include the false teachers of today? Thank you for your thoughts!
"Now John answered Him, saying, "Teacher, we saw someone who does not follow us casting out demons in Your name, and we forbade him because he does not follow us." But Jesus said, "Do not forbid him, for no one who works a miracle in My name can soon afterward speak evil of Me. For he who is not against us is on our side" (Mark 9:38-40).
First, take note of what is not said. The man was casting out demons, but there is no mention of his teaching false doctrine. The only thing John is upset about was the fact that the man was not one of the followers of Jesus. By this, John is not accusing him of not believing in Jesus or not following after the teachings of Jesus; rather, this man wasn't one of their number.
What Jesus is pointing is that if a man is not against Christ, then he must be for Christ. Keep this in mind and look at what John later says, "Whoever transgresses and does not abide in the doctrine of Christ does not have God. He who abides in the doctrine of Christ has both the Father and the Son" (II John 9). Thus, the implication is that when Jesus said that this man was for them, he was teaching proper doctrine that was in accord with what Jesus wanted to be taught. This was not a false teacher who was casting out demons. Think about it. If the man was a false teacher, then by whose power was he casting out demons? It wouldn't have been his own because mere men do not have such power. It couldn't have been God's if he was teaching falsely because God would not have supported a false teacher. Nor could it have been the Devil because demons are on his side anyway (Matthew 12:27-28). The only logical answer is that he was casting out demons by the power of God, and God was lending him strength because he was teaching the truth.
The real lesson being taught is that truth is truth. If a person opened his Bible and learned from its pages what was necessary for salvation and for worshiping God and he began to teach his friends and neighbors and then formed a congregation that followed the teachings of the New Testament, then a church of Christ has been established. It doesn't matter if the man never had seen another church or not. It is the truth that creates it -- nothing more or less. This is why the church has never ceased to exist despite several concerted efforts to suppress it over the centuries. All it takes is an honest heart reading the Bible and it blossoms once again.
This passage also shows that the concept of succession, where a denomination claims to be the "real" church because it can trace its heritage from one church to another all the way back to the apostles is nonsense. While the church spreads rapidly when Christians teach others to follow Christ, it is not a requirement. A person can learn what is needed on their own by simply reading their Bibles and studying its pages. It might go faster with an experienced Christian pointing out the critical areas, but it can be done and has been done independently.