Mark 9:15

Some have suggested that, just as Moses reflected God’s glory after he came down from the mountain, Jesus still showed the glory of his transfiguration. This may explain why the crowd reacted with awe. It is also possible that the crowd responded with awe simply because Jesus returned after being away.

This is the fourth and final time Jesus drives out demons in Mark's Gospel (1:21–28; 5:1–20; 7:24–30). The disciples could not drive out the demon, so Jesus performed the exorcism. This emphasizes the need for faith (see 2:5; 5:34; 10:52). This is another example of the great healing ability of Jesus and of the failure of the disciples (8:32–33; 9:5–7).