Mark 9:14-28 (Also Matthew 17:14-21 and Luke 9:37-43)
Mark gives the most detailed account of this event.
When Jesus came to his disciples, he saw a great multitude about them, and the scribes questioning with them. And immediately all the people, when they saw Jesus, were greatly amazed, and running to him saluted him.
Jesus (to scribes): About what do you question my disciples?
One of the multitude (kneeling down to Jesus – Matthew 17:14): Master, I have brought to you my son (my only child – Luke 9:38), who has a dumb spirit; And wherever the spirit takes him, he tears him: and he foams, and gnashes with his teeth, and pines away: and I spoke to your disciples that they should cast him out; and they could not.
(Matthew 17:15 – Lord, have mercy on my son: for he is a lunatic, and sore vexed)
Jesus: O faithless generation, how long shall I be with you? how long shall I suffer you? bring him to me.
They brought the boy to Jesus: and when the spirit saw Jesus, immediately he tore the boy; and the child fell on the ground, and wallowed foaming.
Jesus: How long is it ago since this came to him?
The father: Of a child. And ofttimes it has cast him into the fire, and into the waters, to destroy him: but if you can do any thing, have compassion on us, and help us.
Jesus: If you can believe, all things are possible to him that believes.
The father (with tears): Lord, I believe; help my unbelief.
I love that part: Lord, help my unbelief.
Jesus saw that the people came running together.
Jesus rebuked the foul spirit: You dumb and deaf spirit, I charge you, come out of him, and enter no more into him.
The spirit cried, and rent the boy sore, and came out of him: and he was as one dead; insomuch that many said, He is dead.
But Jesus took him by the hand, and lifted him up; and he arose.
Matthew 17:18 …and the child was cured from that very hour.
Luke 9:42,43 (excerpts) And Jesus delivered him again to his father. And they were all amazed at the mighty power of God.
Disciples (when Jesus was come into the house): Why couldn’t we cast the spirit out?
Jesus: Because of your unbelief: If you have faith as a grain of mustard seed, you shall say to this mountain, Remove from here to yonder place; and it shall remove; and nothing shall be impossible to you. (Matthew 17:20)
Jesus: This kind can come forth by nothing, but by prayer and fasting. (Mark 9:20-30)
And they departed from there, and passed through Galilee; and he would not that any man should know it.