Matthew 17:18-20

Darby Translation

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

¹⁹ Then the disciples, coming to Jesus apart, said [to him], Why were not *we* able to cast him out?

²⁰ And he says to them, Because of your unbelief; for verily I say unto you, If ye have faith as a grain of mustard [seed], ye shall say to this mountain, Be transported hence there, and it shall transport itself; and nothing shall be impossible to you.