Matthew 17:16

12 But I tell you that Elijah has already come, and they did not recognize him, but have done to him whatever they wished. In the same way, the Son of Man will suffer at their hands.”

13 Then the disciples understood that He was speaking to them about John the Baptist.

14 When they came to the crowd, a man came up to Jesus and knelt before Him.

15 “Lord, have mercy on my son,” he said. “He has seizures and is suffering terribly. He often falls into the fire or into the water.

16 I brought him to Your disciples, but they could not heal him.”

17 “O unbelieving and perverse generation!” Jesus replied. “How long must I remain with you? How long must I put up with you? Bring the boy here to Me.”

18 Then Jesus rebuked the demon, and it came out of the boy, and he was healed from that moment.

19 Afterward the disciples came to Jesus privately and asked, “Why couldn’t we drive it out?”

20 “Because you have so little faith,” He answered. “For truly I tell you, if you have faith the size of a mustard seed, you can say to this mountain, ‘Move from here to there,’ and it will move. Nothing will be impossible for you.”

Read all of Matthew 17