The Gospel According to Saint Matthew

17:14 And when they were come to the multitude, there came to him a
certain man, kneeling down to him, and saying, 17:15 Lord, have mercy
on my son: for he is lunatick, and sore vexed: for ofttimes he falleth
into the fire, and oft into the water.

17:16 And I brought him to thy disciples, and they could not cure him.

17:17 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.

17:18 And Jesus rebuked the devil; and he departed out of him: and the
child was cured from that very hour.

17:19 Then came the disciples to Jesus apart, and said, Why could not
we cast him out?  17:20 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.

17:21 Howbeit this kind goeth not out but by prayer and fasting.