Matthew 17:18-20

Young's Literal Translation

¹⁸ and Jesus rebuked him, and the demon went out of him, and the lad was healed from that hour.

¹⁹ Then the disciples having come to Jesus by himself, said, `Wherefore were we not able to cast him out?'

²⁰ And Jesus said to them, `Through your want of faith; for verily I say to you, if ye may have faith as a grain of mustard, ye shall say to this mount, Remove hence to yonder place, and it shall remove, and nothing shall be impossible to you,