Mark 9:17-19

Then one of the crowd answered and said, “Teacher, I brought You my son, who has a mute spirit. And wherever it seizes him, it throws him down; he foams at the mouth, gnashes his teeth, and becomes rigid. So I spoke to Your disciples, that they should cast it out, but they could not.” He answered him and said, “O faithless generation, how long shall I be with you? How long shall I bear with you? Bring him to Me.”