Matthew 17:10-20

10 So the disciples asked him, "Why do the scribes say that Elijah must come first?"

11 Jesus answered, "Elijah is coming and will put everything in order again.

12 Actually, I can guarantee that Elijah has already come. Yet, people treated him as they pleased because they didn't recognize him. In the same way they're going to make the Son of Man suffer."

13 Then the disciples understood that he was talking about John the Baptizer.

14 When they came to a crowd, a man came up to Jesus, knelt in front of him,

15 and said, "Sir, have mercy on my son. He suffers from seizures. Often he falls into fire or water.

16 I brought him to your disciples, but they couldn't cure him."

17 Jesus replied, "You unbelieving and corrupt generation! How long must I be with you? How long must I put up with you? Bring him here to me!"

18 Jesus ordered the demon to come out of the boy. At that moment the boy was cured.

19 Then the disciples came to Jesus privately and asked, "Why couldn't we force the demon out of the boy?"

20 He told them, "Because you have so little faith. I can guarantee this truth: If your faith is 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."