Mark 9:15-24 NIV
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.”
“You 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 anything, take pity on us and help us.”
“ ‘If you can’?” said Jesus. “Everything is possible for one who believes.”
Immediately the boy’s father exclaimed, “I do believe; help me overcome my unbelief!”
NIV: New International Version