Mark 9:25 (KJV)

And they brought him unto him: and when he saw him, straightway the spirit tare him; and he fell on the ground, and wallowed foaming.

And he asked his father, How long is it ago since this came unto him? And he said, Of a child.

And ofttimes it hath cast him into the fire, and into the waters, to destroy him: but if thou canst do any thing, have compassion on us, and help us.

Jesus said unto him, If thou canst believe, all things are possible to him that believeth.

And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief.

And the spirit cried, and rent him 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.

And when he was come into the house, his disciples asked him privately, Why could not we cast him out?

And he said unto them, This kind can come forth by nothing, but by prayer and fasting.

And they departed thence, and passed through Galilee; and he would not that any man should know it.