Key verse 9: 44b
There are three lessons taught here. First, the Way of the Cross, then humility, and finally universalism. These subjects are important in the path of the disciples.
1. He will be delivered into the hands of men. (43b-45)
The healing of a demoniac was a great feat. Everyone admired Jesus and wanted him to establish the Messianic Kingdom with that power. However, at that moment he taught them once more about the life of Christ. He did the same thing when Peter told him that he was the Christ. Are you able to do what Jesus did and see your misery inspite of your whooping success? This is basic knowledge for the disciples as the World lauds one day but loathes the next.
2. True greatness (46-47)
Everyone wanted to have the first place in God's Kingdom. The 9 other disciples already gnashed their teeth when the first 3 had gone up to the mountain with Jesus. It wasn't very fair, they thought. Jesus taught what their problem was and what true greatness is. They were all too adult-like with too much knowledge, which was not indispensable to them and to God. They had to humiliate themselves like children. From there flows the power of the disciples. The demon child would have been cured.
3. Universalism. (48-50)
The disciples had very petty minds, like the Lion's Club or Freemasons. It was not God's spirit. The Holy Spirit is always open to others. John did not need to stop he who was working in Jesus' name, although he was not directly connected to them. They are still the servants of God and we must recognize them, even if they do not belong to us.