Mark 9:17-19

And one of the multitude answered him, Teacher, I brought unto thee my son, who hath a dumb spirit; and wheresoever it taketh him, it dasheth him down: and he foameth, and grindeth his teeth, and pineth away: and I spake to thy disciples that they should cast it out; and they were not able. And he answereth them and saith, O faithless generation, how long shall I be with you? how long shall I bear with you? bring him unto me.