Matthew 17:14-21 (ESV):

14 And when they came to the crowd, a man came up to him and, kneeling before him, 15 said, “Lord, have mercy on my son, for he has seizures and he suffers terribly. For often he falls into the fire, and often into the water. 16 And I brought him to your disciples, and they could not heal him.” 17 And Jesus answered, “O faithless and twisted generation, how long am I to be with you? How long am I to bear with you? Bring him here to me.” 18 And Jesus rebuked the demon, and it came out of him, and the boy was healed instantly. 19 Then the disciples came to Jesus privately and said, “Why could we not cast it out?” 20 He said to them, “Because of your little faith. For truly, I say to you, if you have faith like a grain of mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move, and nothing will be impossible for you.” 21 But this kind never comes out except by prayer and fasting

Can we conclude from the passage that someone can increase their faith through spiritual practices such as prayer and fasting, to the point that they might even reach a miracle-working faith, capable of casting out troublesome demons with ease, just like Jesus did?

Related question: Is faith a gift or earned through spiritual practices?

  • Verse 21 is not present in all manuscripts.
    – Hg0428
    Commented Dec 11, 2023 at 21:56

5 Answers 5


The reason the disciples were unable to cast out the demons was because their own hearts were not right at that moment. When Jesus had selected only three of them to go with him up the mount of transfiguration, the others, who remained behind, perhaps felt a bit jealous. What we know is simply that they had a dispute among themselves as to whom should be the greatest.

Here is Mark's account of how Jesus discreetly inquired into their controversy a short while after having carefully answered them regarding the need to fast and pray. His first answer laid no blame, nor criticism, though Jesus knew the real cause of their trouble.

And he said unto them, This kind can come forth by nothing, but by prayer and fasting. (Mark 9:29, KJV)

And they departed thence, and passed through Galilee; and he would not that any man should know it. (Mark 9:30, KJV)

For he taught his disciples, and said unto them, The Son of man is delivered into the hands of men, and they shall kill him; and after that he is killed, he shall rise the third day. (Mark 9:31, KJV)

But they understood not that saying, and were afraid to ask him. (Mark 9:32, KJV)

And he came to Capernaum: and being in the house he asked them, What was it that ye disputed among yourselves by the way? (Mark 9:33, KJV)

But they held their peace: for by the way they had disputed among themselves, who should be the greatest. (Mark 9:34, KJV)

Fasting and prayer would have united them. By drawing close to God, and seeking His will, they would have drawn closer to each other, and would have humbled themselves. As it was, with their strivings to be the greatest, they had positioned themselves to take credit for the miracle as if it had been within their own ability or by their own skill. In such a condition, God could not work for them. God would not have been honored if the disciples' own pride and ego had been bolstered by such a "success" on their part.

It was for this reason that both fasting and prayer were necessary in that instance. Essentially, the disciples had lost sight of Christ, and their faith in Christ was marred by their own selfish pride and ambition. They were not in a position to honor Christ, and he could not, therefore honor them. As it is written in 1 Samuel 2:30: "for them that honor me I will honor."

Fasting is not done to make ourselves more worthy, nor to increase our faith--it is to clear our minds so that we can hear God's voice speaking to us. When we know His will, only then are we in a position to follow it.


Matthew 10:

1 Jesus called his twelve disciples to him and gave them authority to drive out impure spirits and to heal every disease and sickness.

Fasting was not a necessary condition for driving out impure spirits.

Elsewhere, Paul advised in 1 Timothy 5:

23 Stop drinking only water, and use a little wine because of your stomach and your frequent illnesses.

Fasting was not a sufficient condition to heal every disease and sickness.

Is Matthew 17:14-21 implying that miracle-working faith can be attained through prayer and fasting?

There is some truth in that but there is no 100% guarantee.

Can we conclude from the passage that someone can increase their faith through spiritual practices such as prayer and fasting, to the point that they might even reach a miracle-working faith, capable of casting out troublesome demons with ease, just like Jesus did?

According to first-order logic, that would be an over-interpretation of the text. We are not Jesus. Fasting would help to some extent but it cannot turn us into a walking Jesus.

  • Then what was the point of fasting on Yom Kippurim in Leviticus 23:28? * "You shall not perform any work on that very day, for it is [Yom Kippurim] for you to gain atonement before YHVH, your God." ( וְכָל־מְלָאכָה֙ לֹ֣א תַֽעֲשׂ֔וּ בְּעֶ֖צֶם הַיּ֣וֹם הַזֶּ֑ה כִּ֣י י֤וֹם כִּפֻּרִים֙ ה֔וּא לְכַפֵּ֣ר עֲלֵיכֶ֔ם לִפְנֵ֖י יְהֹוָ֥ה אֱלֹֽהֵיכֶֽם ) Commented Sep 7, 2021 at 15:19
  • Leviticus 23:28 does not mention fasting :)
    – user35953
    Commented Sep 7, 2021 at 15:33

Matthew 17 has nothing to do with faith. The problem was their unbelief - and the fasting was a means to overcome that (unbelief). Jesus reflects this when He went on to say this wasn’t an issue of ‘faith’ - because even a mustard seed of faith would have been enough.

So any interpretation that looks to find a ‘means’ for ‘increasing faith’ can not use this passage. And I suggest trying to will find no exegetical support elsewhere.

Let’s put this passage into its correct historical perspective. In Marks account of the same incident,

The disciples’ unbelief in this instance was not a disbelief that God’s power could produce deliverance (Luke 9:41), but rather, it was a “natural” kind of unbelief that came from hardened hearts (Mark 6:52) that were more sensitive to what they saw (Mark 9:20) than to what they believed. Mark 9 graphically describes the boy’s seizures.

In Marks account we also find an important ‘key’, missing from Matthew’s account…

MARK 9:17 Then one of the crowd answered and said, “Teacher, I brought You my son, who has a mute spirit.

Casting a demon out of a ‘mute’ person was a ‘sign’, that only the Messiah would be able to perform. Because the ‘method’ or procedure to cast out a demon required asking for its name - and if the person was ‘mute’, then it would ‘fail’ at this step. This being another obstacle leading to unbelief. And this being a possible reason for saying that this kind (mute) could only come out by prayer and fasting.

But either way, ‘faith’ was not the problem, and lack of ‘it’ was not the issue.


There is not a clear cause-effect relationship there, in this particular passage. Moreover, we learn that a strong faith that expels demons can be seen also in those people who are not pleasing Christ at all, that is to say, who are not practicing merciful deeds and do not even know God notwithstanding their miracle-working through invoking His name (Matthew 7:22).

Now, what is the presence of demon in us? It is presence of a fallen angel in us that uses our intellectual and bodily capacities for his pernicious agendum. But had this fallen angel not entered us, and had there been in us a presence of a sinful passion - without any fallen angel being present - that leads us to the same agendum, will any demon bother to enter in us? No, because we are already doing his agendum and he can take a gleeful rest and lay down on his demonic beach and drink his demonic pinna-coladas. Like in an old desert fathers' stories: two demons are walking in a desert, one experienced and another - novice; so, they see a drunken monk and the novice excitingly says to the experienced demon: "Let us seduce him and make a trick on him!" The experienced one retorts: "You, stupid, he is already ours, let us seduce the one who is sober, fasting and praying!"

So, not so much demons, but our sinful passions and inclinations are of the primary importance. Even if all demons are driven out from our galaxy, the humanity will not be any better or happier, for the sinful passions will remain all the same: they will have the same percentage and power on the earthly populations. Will not a plagiarist plagiarize without demons' seduction? Will not a naughty journalist write a rigged article for money without demons' seduction? Will not a womanizer lead a lewd life without demons forcing him to? Yes, yes and yes! So, it is important to fight passions and if you defeat passion, you have also defeated demon for demon grazes only on grass of our sinful passions and if we eradicate this grass through fasting and prayers, there will be nothing for demons to graze inside us.

Yes, one can expel demon and this act of expulsion will not make him, the expulsor himself any better person and closer to Christ, and contrary, one can fight one's sinful passions through prayers and fasting without working any miracle, and this will make him closer to Christ.

Eventually, of course, the one who is thus close to Christ by the reason of defeating one's sinful passions through prayers and fasting will be more entitled also to be granted by God the power to help others and also the power of expelling demons, if this last ability, which is a miracle-working ability will not make him turgid and arrogant. God usually wards even His chosen ones from miracle-working abilities in order to protect them from turgidness and arrogance. Because of this divine protection even Paul, the seer of the Third Heaven, was not granted expulsion of one naughty demon not only from others, but even from his own self, for so much God loved him and so much He wanted him to remain humble (2 Cor. 12:8-10), that He made even demon immune from Paul's prayers and let it remain in His "chosen vessel" (Acts 9:15).

Just imagine, how dangerously arrogant and self-aggrandized you yourself, who are now reading this, will turn, had you worked even one tiny miracle, if even Paul was not immune from this peril?!


I think the text is fairly straightforward and clear. Yes, unbelief blocks faith, and faith is necessary to perform miracles. The part about prayer and fasting refers to the process of getting nearer to God and putting off of the flesh. So yes, prayer and fasting does increase your faith and submission to God, allowing God to perform greater miracles through you. Here’s a scriptural example: before Jesus began His ministry, what did He do?—He went into the wilderness and fasted and prayed 40 days! Immediately after He began His ministry He began casting out demons, healing, and miracles of all kinds. He was on fire!

John 14:12 KJV

Verily, verily, I say unto you, He that believeth on me, the works that I do shall he do also; and greater works than these shall he do; because I go unto my Father.

If He didn’t mean what He said, then what did He mean? I have witnessed this in myself and I have heard testimonies from other Christians on the order of healings, miracles, and especially for this context, the casting out of demons and deliverance.