Matthew 17:11-21

11 And Jesus answered and said to them, Elijah truly will first come, and restore all things:

12 But I say to you, that Elijah is come already, and they knew him not, but have done to him whatever they pleased: likewise will also the Son of man suffer by them.

13 Then the disciples understood that he spoke to them concerning John the Baptist.

14 And when they had come to the multitude, there came to him a [certain] man kneeling down to him, and saying,

15 Lord, have mercy on my son; for he is lunatic, and grievously distressed; for often he falleth into the fire, and often into the water.

16 And I brought him to thy disciples, and they could not cure him.

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

21 However, this kind goeth not out, but by prayer and fasting.