Here’s an interesting thought.
‘Teacher,’ said John, ‘we saw someone casting out demons in your name. We stopped him, because he wasn’t following us.’
‘Don’t stop him,’ said Jesus. ‘No one who does powerful things by my name will be able to say bad things about me soon afterwards. Anyone who’s not against us is on our side. Anyone who even gives you a cup of water in my name, because you belong to the Messiah – I’m telling you the truth, that person won’t go unrewarded.
Jesus, Mark 9 vv. 38-41.
Tom Wright, The New Testament for Everyone