Matthew 17:17-20

17 Then Jesus answered and said, O faithless and perverse generation, how long shall I be with you? how long shall I suffer you? bring him hither to me.

18 And Jesus rebuked the devil; and he departed out of him: and the child was cured from that very hour.

19 Then came the disciples to Jesus apart*, and said, Why could not we cast him out?

20 And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove; and nothing shall be impossible unto you.