Matthew 17:14-19

14And when they had come to the multitude, there came to him a certain man, kneeling down to him, and saying, 15Lord, have mercy on my son: for he is lunatic, and greatly distressed: for often he falleth into the fire, and often into the water. 16And I brought him to thy disciples, and they could not cure him. 17Then Jesus answered and said, O faithless and perverse generation, how long shall I be with you? how long shall I bear with you? bring him here to me. 18And Jesus rebuked the demon; and he departed out of him: and the child was cured from that very hour. 19Then came the disciples to Jesus privately, and said, Why could not we cast him out?