Matthew 17:18-20

18And Jesus rebuked him, and the demon came out of him, and the boy was healed 1at once.

19Then the disciples came to Jesus privately and said, “Why could we not cast it out?” 20And He said to them, “Because of your meager faith; for truly I say to you, 2if you have faith 3the size of 4a mustard seed, you will say to 5this mountain, ‘Move from here to there,’ and it will move; and 6nothing will be impossible for you.7”