Jesus comes down from the mount of transfiguration to discover his disciples are involved in a dispute with the Scribes. A crowd have gathered who are greatly amazed (ἐξεθαμβήθησαν) when they see Him. Some commentators have suggested that it is because Jesus face is still shining from the transfiguration. However this text makes sense without this interpretation as people were no doubt excited to see a man whom so many have talked about. Jesus ministry is gaining popular approval .
Jesus seeks to find out the cause of the dispute. The focus of the story now switches from that of groups (disciples, scribes, crowds) to the plight of a father whose son has a ‘spirit that makes him mute’. The father had sought help from the disciples but they were not able to cast out the spirit. The stage has been set, Is Jesus greater than his disciples? Is Jesus able to do what the disciples could not? The desciples lacked strength (οὐκ ἴσχυσαν ), will Jesus?
Jesus does not immediately heal the boy but calls the generation unbelieving (ὦ γενεὰ ἄπιστος ). Mark’s gospel is full of sayings about faith/belief. See 2:5, 4:40, 5:34, 19:52, 11:22-23). Jesus accuses the generation of being unbelieving. One is reminded of Deut 32:5, Numbers 14:11 and Is 65:2 which speaks of the rebellion of God’s own people. Jesus came to heal and restore and bring the kingdom. He also offered a challenge to those who were living lives of rebellion.
The boy was brought to Jesus and the spirit took over the boy. The presence of Jesus causes evil to raise its head. (Mark 1:23-26, 34, 3:11-12, 5:6-13). Jesus looks to the father for faith, in contrast to the faithlessness of the generation. The man is weak in faith, perhaps due to numerous failed visits he had made with exorcists and the inability of the disciples.
True faith is always aware how small and inadequate it is. The father becomes a believer not when he amasses a sufficient quantum of faith but when he risks everything on what little faith he has, when he yields his insufficiency to the true sufficiency of Jesus, “ ‘I do believe; help me overcome my unbelief!’ ” The risk of faith is more costly to the father than bringing his son to Jesus, for he can talk about his son but he must “cry out” (Gk. krazein) for faith.103 True faith takes no confidence in itself, nor does it judge Jesus by the weakness of his followers. It looks to the More Powerful One (1:7) who stands in the place of God, whose authoritative word restores life from chaos. True faith is unconditional openness to God, a decision in the face of all to the contrary that Jesus is able.
Edwards, James R.: The Gospel According to Mark. Grand Rapids, Mich; Leicester, England : Eerdmans; Apollos, 2002 (The Pillar New Testament Commentary), S. 278
Jesus commands the spirit in the first person (I command you) and it is not in the name of YHWH or one of the prophets. Jesus has power, he could do what others could not. He has authority.