Matthew 17:7, 20-21

Then Jesus came and touched them and said, Arise and be not afraid.

And Jesus said unto them, Because of your unfaithfulness; for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove from here to yonder place, and it shall remove; and nothing shall be impossible unto you. Howbeit this lineage of demons does not go out but by prayer and fasting.