‘Whoever is not against us is for us’ says Jesus to his disciples. The context was that a person other than the twelve disciples was going off to do his own mission for Jesus. The disciples were concerned that this unauthorised and untrained activist would bring Jesus into disrepute.
However, you can hear the jealousy and insecurity in their charges. Jesus was secure in allowing his Father to operate through anyone. Ultimately, he had his eye to the future when he was taken from the earth and any believer would be qualified through faith. The disciples were keen to protect the status that ministry offered them.
Today, all kinds of people do the work of God, many of whom we would not easily get along with. They are not against the kingdom of God, therefore they are for us. Thinking that we are the only true agents of God in this world harms our view and participation in the body of Christ. It also hampers the good news spreading and more people being liberated.