Luke 9:41

And Jesus answered and said, O faithless and perverse generation, how long shall I be with you, and bear with you? bring hither thy son.

Jesus was displeased with the apostles' failure, also by the Pharisees' campaign of allegation that Elijah had not come, an objection he had just answered for Peter, James, and John (Matthew 17:9-13); and also by the insinuation of the afflicted child's father that perhaps not even Jesus could heal his son (Mark 9:23). Satan had clearly made some headway, leading to the denunciation here by Jesus.