|Mark 9:14 And when he came to his disciples, he saw a great multitude about them, and the scribes questioning with them. 15 And straightway all the people, when they beheld him, were greatly amazed, and running to him saluted him. 16 And he asked the scribes, What question ye with them? 17a And one of the multitude answered and said,||Matt 17:14 And when they were come to the multitude, there came to him a certain man, kneeling down to him, and saying,||Luke 9:37 And it came to pass, that on the next day, when they were come down from the hill, much people met him. 38a And, behold, a man of the company cried out, saying,|
|Mark 9:17b Master, I have brought unto thee my son, which hath a dumb spirit; 18 And wheresoever he taketh him, he teareth him: and he foameth, and gnasheth with his teeth, and pineth away: and I spake to thy disciples that they should cast him out; and they could not.||Matt 17:15 Lord, have mercy on my son: for he is lunatick, and sore vexed: for ofttimes he falleth into the fire, and oft into the water. 16 And I brought him to thy disciples, and they could not cure him.||Luke 9:38b Master, I beseech thee, look upon my son: for he is mine only child. 39 And, lo, a spirit taketh him, and he suddenly crieth out; and it teareth him that he foameth again, and bruising him hardly departeth from him. 40 And I besought thy disciples to cast him out; and they could not.|
|Mark 9:19 He answereth him, and saith, O faithless generation, how long shall I be with you? how long shall I suffer you? bring him unto me.||Matt 17:17 Then Jesus answered and said, O faithless and perverse generation, how long shall I be with you? how long shall I suffer you? bring him hither to me.||Luke 9:41 And Jesus answering said, O faithless and perverse generation, how long shall I be with you, and suffer you? Bring thy son hither.|
Mark 9:20 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.
Mark 9:21a And he asked his father, How long is it ago since this came unto him?
Mark 9:21b And he said, Of a child. 22 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.
Mark 9:23 Jesus said unto him, If thou canst believe, all things are possible to him that believeth.
Mark 9:24 And straightway the father of the child cried out, and said with tears, Lord, I believe; help thou mine unbelief.
|Mark 9:25 When Jesus saw that the people came running together, he rebuked the foul spirit, saying unto him, Thou dumb and deaf spirit, I charge thee, come out of him, and enter no more into him.||Matt 17:18a And Jesus rebuked the devil;||Luke 9:42a And as he was yet a coming, the devil threw him down, and tare him. And Jesus rebuked the unclean spirit,|
|Mark 9:26 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. 27 But Jesus took him by the hand, and lifted him up; and he arose.||Matt 17:18b and he departed out of him: and the child was cured from that very hour.||Luke 9:42b and healed the child, and delivered him again to his father.|
Luke 9:43a And they were all amazed at the mighty power of God.
|Mark 9:28 And when he was come into the house, his disciples asked him privately, Why could not we cast him out?||Matt 17:19 Then came the disciples to Jesus apart, and said, Why could not we cast him out?|
|Mark 9:29  And he said unto them, This kind can come forth by nothing, but by prayer and fasting.||Matt 17:20 And Jesus said unto them, Because of your unbelief: for verily I say unto you, If ye have faith as a grain of mustard seed, ye shall say unto this mountain, Remove hence to yonder place; and it shall remove ; and nothing shall be impossible unto you. 21 Howbeit this kind goeth not out but by prayer and fasting.||Luke 17:5 And the apostles said unto the Lord, Increase our faith. 6 And the Lord said, If ye had faith as a grain of mustard seed, ye might say unto this sycamine tree, Be thou plucked up by the root, and be thou planted in the sea; and it should obey you.|
Mark seems to be saying that the disciples couldn't cast out the devil because they were using the wrong methods, while Luke attribute the disciples' failure to lack of faith. Matthew's explanation for the disciple's failure is a combination of both method and faith.
The ability to move a mountain with faith is also mentioned in Mark 11:23, Matthew 21:21 and Luke 17:6.