Jesus had just come from the glory of the mountain into a scene of failure and unbelief. The disciples could not help the boy, even though Jesus had earlier given them "power and authority over all devils" (Luke 9:1). His question is a lament over that unbelief.

Commentators differ on whom He meant. Gill says the words were aimed at the unbelieving Jews, especially the scribes and Pharisees, who had been "insulting the disciples, and triumphing over them." Barnes, on Matthew 17:17, says Jesus applied it "probably to the Jews, and not to his real disciples," though he adds that even the disciples were slow to trust Him. Matthew Henry takes it as Christ reproving the disciples for their weak faith, and quotes Dr. Clarke, who also hears it as spoken to them: "Will ye be yet so faithless and full of distrust that ye cannot execute the commission I have given you?" Either way, unbelief is what grieved Him.

Jesus did not wait for an answer. In the same breath He said, "Bring thy son hither" (Luke 9:41). As the boy came, "the devil threw him down, and tare him." Jesus "rebuked the unclean spirit, and healed the child, and delivered him again to his father" (Luke 9:42). The people "were all amazed at the mighty power of God" (Luke 9:43). In Matthew, when the disciples later asked why they could not cast it out, Jesus said, "Because of your unbelief" (Matthew 17:19-20).

"Faithless" translates apistos, meaning unbelieving. "Perverse" translates diestrammene, a form of a verb meaning to twist or distort; the ESV renders it "twisted." "Suffer you" translates anexomai, "bear with" or "put up with."

Matthew and Mark split Jesus' words into two questions: "how long shall I be with you? how long shall I suffer you?" (Matthew 17:17; Mark 9:19). Mark adds that the scribes had been questioning the disciples before Jesus arrived (Mark 9:14).

This question shows both sides of Jesus' heart. He felt the weight of unbelief and said so honestly. Yet His very next words were "Bring thy son hither." His grief over unbelief did not make Him turn away from a father and a suffering child.

The question also comes as His death draws near. He had foretold that He must be slain (Luke 9:22), and on the mountain Moses and Elias spoke of "his decease which he should accomplish at Jerusalem" (Luke 9:31). Right after the healing He told His disciples, "the Son of man shall be delivered into the hands of men" (Luke 9:44).