In this text are several events that take place right after the Transfiguration. First, as they were coming down the mountain a crowd gathers to meet Jesus. When they arrive, there is a man whose son has been inflicted by demonic possession and he begs Jesus for help. His disciples seemed to have tried already to handle the situation without success, but Jesus, expressing a little bit of frustration says the word, and the demon is gone (9:37-43).
Right after that, Jesus once again tells the disciples that He is going to be killed at the hands of men, but they don’t understand Him and are afraid to ask (9:43b-45). Notice how much of a contrast this is with His having just dealt so easily with the forces of demons. In these two incidents Jesus demonstrated to them His identity as the Son of God and His mission as Messiah, having on one hand divine authority over spiritual forces, and predicting on the other hand His work on the cross.
Then the disciples begin to debate which of them is the greatest Hello, are you boys paying attention?
Who can blame them; this is a lot to get your head around. Jesus sets a little child in front of them and says: “Whoever welcomes this little child in my name welcomes me; and whoever welcomes me welcomes the one who sent me. For it is the one who is least among you all who is the greatest.” (9:48b) The little child has nothing to offer, no money, no position, no particular social importance and is entirely vulnerable, at least in an earthly sense. The one, who will be great in the Kingdom, is the one who is least in this world. With this, Jesus has not only revealed His nature and purpose, but theirs as well.
Finally, John tells Jesus that they saw a guy driving out demons in Jesus’ name and they told him to stop, since the man wasn’t “one of us”. Jesus’ reply to that bit of information?
“Do not stop him,” Jesus said, “for whoever is not against you is for you.” (9:50)
The time of conflict had come, and from this point forward, Jesus would be viewed as ‘extreme and out of the mainstream’ and the full force of the establishment would be turned against Him.