Mark 9:17-19

And one of the crowd answered Him, “Teacher, I brought You my son, possessed with a spirit which makes him mute; and whenever it seizes him, it slams him to the ground and he foams at the mouth, and grinds his teeth and stiffens out. I told Your disciples to cast it out, and they could not do it.” And He *answered them and *said, “O unbelieving generation, how long shall I be with you? How long shall I put up with you? Bring him to Me!”