Mark 9:33-40

33 He came to Capernaum, and when he was in the house he asked them, “What were you arguing among yourselves on the way?”

34 But they were silent, for they had disputed one with another on the way about who was the greatest.

35 He sat down, and called the twelve; and he said to them, “If any man wants to be first, he shall be last of all, and servant of all.”  36 He took a little child, and set him in the midst of them. Taking him in his arms, he said to them,  37 “Whoever receives one such little child in my name, receives me, and whoever receives me, doesn't receive me, but him who sent me.”

38 John said to him, "Teacher, we saw someone who doesn't follow us casting out demons in your name; and we forbade him, because he doesn't follow us."

39 But Jesus said, “Don't forbid him, for there is no one who will do a mighty work in my name, and be able quickly to speak evil of me.  40 For whoever is not against us is on our side.