When they came to the other disciples, they saw a large crowd around them and the teachers of the law arguing with them. As soon as all the people saw Jesus, they were overwhelmed with wonder and ran to greet him.
“What are you arguing with them about?” he asked.
A man in the crowd answered, “Teacher, I brought you my son, who is possessed by a spirit that has robbed him of speech. Whenever it seizes him, it throws him to the ground. He foams at the mouth, gnashes his teeth and becomes rigid. I asked your disciples to drive out the spirit, but they could not.”
“O unbelieving generation,” Jesus replied, “how long shall I stay with you? How long shall I put up with you? Bring the boy to me.”
So they brought him. When the spirit saw Jesus, it immediately threw the boy into a convulsion. He fell to the ground and rolled around, foaming at the mouth.
Jesus asked the boy’s father, “How long has he been like this?”
“From childhood,” he answered. “It has often thrown him into fire or water to kill him. But if you can do something, take pity on us and help us.”
” ‘If you can’?” said Jesus. “Everything is possible for him who believes.”
Immediately the boy’s father exclaimed, “I do believe: help me overcome my unbelief!”
When Jesus saw that a crowd was running to the scene, he rebuked the evil spirit. “You deaf and mute spirit,” he said, “I command you, come out of him and never enter him again.”
The spirit shrieked, convulsed him violently and came out. The boy looked so much like a corpse that many said, “He’s dead.” But Jesus took him by the hand and lifted him to his feet, and he stood up.
After Jesus had gone indoors, his disciples asked him privately, “Why couldn’t we drive it out?”
He replied, “This kind can come out only by prayer.”
Here we have an example of Jesus casting out a demon. Whereas Matthew emphasized Jesus’ teachings and Luke emphasized Jesus’ healings, Mark emphasized the casting out of demons. This is because he was concerned with showing Jesus as establishing the Kingdom of God. By casting out demons Jesus was visibly demonstrating his authority over all spiritual forces, showing that the kingdom of this world was over and a new kingdom was beginning. Such an emphasis would surely have had traction with the believers in Mark’s community, presumably in and around Rome, who were dealing with intense persecution for their non-acceptance of the claims of Roman power and who would be buoyed by the news that the evil powers of this world were defeated in Christ.
A point to notice here: Every time Jesus performs a healing or exorcism, he always places the people who witness it under strict orders to not tell anyone about it. This is largely because he does not want to attract attention for the wrong reasons. At this point in the story he is already having to take a detour to avoid a region where the people were determined to make him king by force and where others were just as strongly opposed to him. Jesus is determined to not be the Messiah that everyone thinks he should be, and no one thinks that the Messiah should die on a cross. Yet Jesus is intentionally moving toward that, and he is resolutely avoiding any path to glory that bypasses the cross. For this reason, he remains hush-hush about his identity as the Son of God until the time for the cross has come. So here, when it becomes clear that a crowd is gathering to see what is going on, he goes on and heals the boy and gets out of there.
Another point here: In verse 19 Jesus laments “O unbelieving generation…how long shall I stay with you? How long shall I put up with you?” Notice the exasperation with the disciples’ lack of faith that drips through here. We believe in a Jesus who is fully human and fully divine, but does our view of Jesus have room for a Jesus who feels this level of exasperation at not being fully understood by those closest to him?