Mark 9:17-20

And someone from the crowd answered him, “Teacher, I brought my son to you, for he has a spirit that makes him mute. And whenever it seizes him, it throws him down, and he foams and grinds his teeth and becomes rigid. So I asked your disciples to cast it out, and they were not able.” And he answered them, “O faithless generation, how long am I to be with you? How long am I to bear with you? Bring him to me.” And they brought the boy to him. And when the spirit saw him, immediately it convulsed the boy, and he fell on the ground and rolled about, foaming at the mouth.