Coming to the disciples, he saw a great multitude around them, and scribes questioning them. Immediately all the multitude, when they saw him, were greatly amazed, and running to him, greeted him. He asked the scribes, “What are you asking them?”
One of the multitude answered, “Teacher, I brought to you my son, who has a mute spirit; and wherever it seizes him, it throws him down; and he foams at the mouth, grinds his teeth, and becomes rigid. I asked your disciples to cast it out, and they weren’t able.”
He answered him, “Unbelieving generation, how long shall I be with you? How long shall I bear with you? Bring him to me.”
They brought him to him, and when he saw him, immediately the spirit convulsed him and he fell on the ground, wallowing and foaming at the mouth.
He asked his father, “How long has it been since this has been happening to him?” He said, “From childhood.
Often it has cast him both into the fire and into the water to destroy him. But if you can do anything, have compassion on us and help us.”
Jesus said to him, “If you can believe, all things are possible to him who believes.”
Immediately the father of the child cried out with tears, “I believe. Help my unbelief!”
When Jesus saw that a multitude came running together, he rebuked the unclean spirit, saying to him, “You mute and deaf spirit, I command you, come out of him, and never enter him again!”
After crying out and convulsing him greatly, it came out of him. The boy became like one dead, so much that most of them said, “He is dead.” But Jesus took him by the hand and raised him up; and he arose.
When he had come into the house, his disciples asked him privately, “Why couldn’t we cast it out?”
He said to them, “This kind can come out by nothing but by prayer and fasting.”
Coming down, Jesus finds his other disciples in an argument with scribes, having failed to drive a spirit out of a boy who suffers violent seizures. The father asks Jesus for help 'if you can'; Jesus replies that all things are possible to one who believes, and the father cries, 'I believe; help my unbelief.' Jesus drives out the spirit and raises the boy.
What does this mean?
A 'dumb spirit' (KJV) is one that makes him unable to speak. 'Teareth him' means throws him into convulsions; 'pineth away' means becomes rigid. 'Faithless generation' means unbelieving generation.
Historical context
The symptoms resemble what is now called epilepsy, a condition widely attributed in the ancient world to spirits; Matthew's version uses a word meaning 'moonstruck' (Matthew 17:15). A few important early manuscripts of verse 29 read only 'by prayer', without 'and fasting'.
Why does it matter?
The father's honest mixture of faith and doubt is one of Mark's most memorable moments. The contrast with the glory on the mountain is sharp: the disciples who stayed below are powerless. The boy who seems dead and is 'raised' anticipates the language of resurrection.
Editorial notes, not scripture.