The casting out of demons is one of the signs that Jesus promised would follow all believers:

Mark 16:17 (KJV):

17 And these signs shall follow them that believe; In my name shall they cast out devils; they shall speak with new tongues;

In fact, these signs are examples of the power conferred to believers by the Holy Spirit (Matthew 12:28, Acts 1:7-8, 1 Corinthians 2:4-5, Romans 15:17-19).

However, although the Holy Spirit is the one giving the power, there appears to be some work to be done on the believer's side. Concretely, Matthew 17:16-21 (KJV) says:

16 And I brought him to thy disciples, and they could not cure him. 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. 18 And Jesus rebuked the devil; and he departed out of him: and the child was cured from that very hour. 19 Then came the disciples to Jesus apart, and said, Why could not we cast him out? 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.

Why do believers have to pray and fast to be able to cast out certain kinds of demons? In what manner do the praying and the fasting by the believer contribute to the outcome? Isn't the power of the Holy Spirit alone enough?

  • 1
    Where is Mark 16:17 in the original Codex Sinaiticus? Did Mark 16 not originally stop at verse 8? Commented Oct 27, 2020 at 15:03
  • Sorry, but the expression "higher rank demons" used in your question is an illegitimate introduction of an information in the text of the New Testament, which information is not there, at least, directly. In fact, "this kind" can mean not any higher kinds of demons, but "this kind [of creatures]", implying the entire class of demons, all of them. You have first to make exegetical efforts to prove that "this kind" means a section of demonic population, and even that of an elite of that population, for it is not necessary that the demons needing fasting and prayer are elite and not plebs. Commented Oct 28, 2020 at 14:49
  • @LevanGigineishvili good point, maybe "certain demons" would be more appropriate?
    – user38524
    Commented Oct 28, 2020 at 15:35
  • @SpiritRealmInvestigator For me most plausible is the traditional interpretation that γένος here denotes the entire population of all demons. And it seems also logically more consistent, for Jesus can immediately expel all demons, but He also ordained human participation in this expulsion through prayers and fasting; now, as the immediate expulsion by Jesus relates to all demons, so also the human-participatory expulsion of demons from themselves, most plausibly, also relates to all demons. But I admit that some demons can be more vicious than others, no question about that! (cf Matthew 12:45) Commented Oct 28, 2020 at 19:33

7 Answers 7


In γένος all demons, their entire universe is implied, as the traditional interpretation has it. For instance, if I see a tennis player blaming everybody and everything except for himself for having lost a match, I can say: "This tribe always finds fault in others, not in themselves", I will mean in "this tribe" all tennis players without exception, and I know I am right, myself being one of that tribe also. Indeed, Jesus has authority to expel all demons at an eyewink, and He has given this same authority to His disciples to the effect that they also can expel all demons vicariously, for otherwise Jesus would not have reprimanded His disciples for their lack of faith and for not expelling the demon from the boy (Mark 9:19).

But He also said that demons are to be expelled not immediately (which is also possible, as noted above), but through prayers and fasting. But what does it mean? To answer this question, we have to understand what it is to be possessed by demon? It is an intense form of being a slave of a sinful passion. In fact, our sinful passion is a pasture of a demon specialised in this sin. For instance, if we are sexually lewd and cannot overcome a desire to be engaged in lewd sexual exploits, then we are possessed also by a demon of lust. To give an example: if I put honey on a table, then it will attract flies; our sinful passion is a 'honey'-like attraction for demons who light upon our sinful passion as a fly upon a honey drop. Now, to eliminate this sinful "honey" in ourselves, this presence of attraction towards and delectation of sin in ourselves we need to engage in ascetic exploits of prayers and fasting, which attracts the working of divine Grace in us and this working gradually eliminates in us the sinful inclination. Now, if the sinful inclination is defeated in us, then demon cannot touch us for he has lost any pasture in us and this demon will go to light upon another human who will attract him (this demon) through his or her sinful passion.

Thus, even if demon can be expelled by God's miracle immediately, it is impossible even for a divine miracle to expel from us a sinful inclination unless we collaborate with God's working in us, and this is through prayers and fasting. Thus, unless this sinful inclination is defeated in us, we are always vulnerable for the demonic attack and presence. Moreover, even if God annihilates all demons, but we will not fight out our sinful passion through fasting and prayers, the non-existence of demons will not ameliorate our wretched condition even a tiny bit! We are in hell if we are under a power of sin and what difference there is if we stay in hell in a company of demons or without them, hell is hell with all that!

  • So are you saying that the one to pray and fast is the demonized? I thought Jesus' recommendation to pray and fast was aimed at those responsible for casting out demons, not the demonized themselves.
    – user38524
    Commented Oct 30, 2020 at 19:17
  • @SpiritRealmInvestigator If I cannot help cheating, then I do not have to bother about demons in other people, for I have myself a demon of lying in myself which I have to fight away through an ascetical practice of trying not-lying and praying for divine power to overcome it. If I defeat this passion in myself, gradually, then a demon of lying will be very much disappointed to have lost a pasture in me and will go to light upon another person, another victim of a passion of lying in whom he will find a good and appropriate host. Commented Oct 30, 2020 at 19:26

In the parable of the widow and the unjust judge Jesus teaches us to “pray always and not to lose heart (Lk 18:1-8). The question then is not when do we need to pray, but whether there is ever a time or situation that doesn’t call for our prayers. Like the unrelenting widow or the friend who knocks again and again on your door at midnight (Lk 18:1-8, Lk 11:5-8), we are called to pray always and with perseverance.

And we need to pray with faith. That faith doesn’t have to be great, and like the father of the boy, we may still harbor “unbelief,” but ours needs to be a faith that is living (Mk 9:24). Like the tiny mustard seed, it needs to be tended and given the right conditions to sprout and grow.

  • “For truly I tell you, if you have faith the size of a mustard seed, you will say to this mountain, ‘Move from here to there,’ and it will move; and nothing will be impossible for you.” (Mt 17:20)
  • Jesus answered them, “Truly I tell you, if you have faith and do not doubt, not only will you do what has been done to the fig tree, but even if you say to this mountain, ‘Be lifted up and thrown into the sea,’ it will be done. Whatever you ask for in prayer with faith, you will receive.” (Mt 21:21-22)

That faith and prayer go hand in hand seems hardly worth mentioning. Are they not central to the life of discipleship? Yet why does Jesus need to remind us to pray always, with faith and perseverance? Isn’t it because sometimes our faith is dry and lifeless and our prayers, lacking? At other times, life’s obstacles may seem unsurmountable or the demons in our life seem too great, and we “lose heart.” Like the father of the possessed boy, we might even wonder whether there is anything that God can do (Mk 9:24). At such times, we are called to follow Jesus’ example: “In his anguish he prayed more earnestly” (Lk 22: 44).

  • Good points. But how do prayer and fasting enter the picture?
    – user38524
    Commented Oct 28, 2020 at 15:45

Simple answer - they don’t. Jesus did not say that the reason these disciples could not cast this demon out was because they didn’t have faith but rather because they had unbelief. Demons are not driven out via prayer and fasting

This story recorded in Matthew and Mark has been traditionally misinterpreted namely to ‘fit personal doctrine/theology’. Let’s look a little closer.....

MAT 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.

The disciples’ unbelief here was not a disbelief that God’s power could produce deliverance, but rather, it was a “natural” kind of unbelief that was more affected by their senses’, that is, what they saw (Mark 9:20) rather than to what they believed.

Neither was It because of lack of faith - you only need a ‘mustard seed size’ to move a mountain.

MAT 17:21 Howbeit this kind goeth not out but by prayer and fasting.

The context for verse 21 is verse 20, that is, the ‘subject’ is unbelief. Prayer and fasting do not drive out ‘certain’ demons. This kind of ‘unbelief’, which originates from the 5 senses, can be overcome, driven out by fasting, which teaches you to deny what your senses are telling you.

  • So in a way prayer and fasting do help to cast out demons "indirectly" or "by transitivity". Prayer and fasting -> overcoming unbelief -> being able to cast out demons. Is this reasoning correct?
    – user38524
    Commented Oct 28, 2020 at 16:08
  • @Spirit Realm Investigator Prayer and fasting are always for ‘you’ - every time. Prayer and fasting simply can’t ‘move’, nor ‘change’ anyone/anything else - including God. That practice changes you. It’s for your benefit.
    – Dave
    Commented Oct 28, 2020 at 18:40
  • And by changing you they enable you to cast out demons you weren't able to cast out before, correct?
    – user38524
    Commented Oct 28, 2020 at 20:21
  • @Spirit Realm Investigator Yes. Comes down to faith - everything ‘comes’ and ‘works’ by ‘faith’. Everything. And faith can’t work with ‘unbelief’. Hence ‘fasting’ is still a valid practice. (Although these days dealing with demons should not necessarily be ‘modeled’ on what we see in the gospels - but that’s another topic.)
    – Dave
    Commented Oct 28, 2020 at 22:12
  • 1
    @Dave Demons block Christ’s presence in us, but they can do so only through our sinful passions, which form a pasture for them to graze. Now, you can fight and overcome a sinful passion – lust, gluttony, envy etc. – through prayers and fasting, and only through them, in fact. Thus, if I succeed to overcome a sin in my soul, then demon cannot graze in my soul, because his pasture there is annihilated. Then how you can say that ‘prayer and fasting do not cast out demons”? Formula of desert fathers: “more difficult to defeat a passion than a demon; you defeat passion=you defeat demon”. Commented Oct 31, 2020 at 7:08

An insight, some background, and a bit of supposition might bring some perspective in answer to this question.

And to simplify things, I'll focus on the Mark account.

The insight comes when we ask where prayer showed up in the expulsion of the demon. Jesus said that kind of demon can't come out but by prayer. Jesus then cast out the demon. So who prayed?

I believe the father prayed when he asked Jesus to cast out the demon (Mark 9:17-18). Jesus is God. When the man didn't find help from the disciples, he went directly to Jesus. That's the prayer.

Based on this insight, a preliminary answer to the question, why prayer and fasting are necessary, is that there are certain kinds of demons that only God/Jesus can cast out, not the disciples. So ask God to do it, don't ask men.

Now, some background. When Jesus gives the Holy Spirit, he doesn't make us as powerful as God, as if every demon including Satan must quake in our presence. Indeed, I think it all makes sense more when we look at exorcism as a matter, not of power, but of authority.

In Mark 6:7, in preparation for the Galilean ministry, Jesus gave his disciples authority over evil spirits.


He didn't give them muscles, he gave them rank. Evil spirits would still be more powerful in a tug-of-war, or in bringing sickness, or foaming at the mouth; but the disciples now were given, so to speak, Colonel rank whereas most evil spirits were Sergeants and Privates.

When considering authority, it is conceivable that the disciples might encounter an evil spirit with a higher rank, so prayer in those cases is needed to appeal to Christ, who has the highest rank/authority of all. Consider Michael in Jude 9, who was doing God's will, who was properly authorized to a task, but was either outranked, or of equal rank with Satan, so he called on God to rebuke Satan rather than using his own authority.

The supposition, then is to fit faith into this situation. I think that greater faith would not result in greater authority. No, the authority had been given by the Lord. He didn't dole out authority based on faith (or presumably, Judas would not have been given any authority to cast out demons, and doubting Thomas may have been given only meager authority). No, Jesus gave an assignment, then gave authority equal to the task.

Lack of faith could certainly keep someone from using his authority, however. Faced with an evil spirit who shrieked, convulsed the child, then made it appear that the child was dead (Mark 9:26), it would be easy to think the task was too great. (They had authority to cast out demons, not raise the dead?) Lack of faith looks at the powerful storm waters, and forgets spiritual authority, which is the command of Jesus to step out of the boat. Faith looks past the powerful flooding Jordan, and steps into the water with the full authority of God, then watches the waters part. So faith may be necessary to keep us focused to use our authority in obedience to Christ.

A second way lack of faith would matter, is the case where our authority seems to be insufficient to the task. In those cases lack of faith would lead to failure and despair, but faith would lead us to call out to God for help - in other words, prayer. In the same way that faith led the father to come to Jesus for help, even after the disciples' failure, and that was his prayer; even so the disciples, after their failure, could have called out to God in prayer, to receive God's help.

  • It's a good answer - very nearly upvoted this, but it's currently weighted too heavily on "insight" and "supposition", and lacks sources. If you could supply other passages or early Christian sources supporting this interpretation, you could shape this into a more conclusive answer.
    – Steve can help
    Commented Oct 30, 2020 at 6:30

"The casting out of demons is one of the signs that Jesus promised would follow all believers:"

"In my name they shall cast oute devyls and shall speake with newe tonges" (Mark 16:17; Tyndale Bible of 1526)

It is interesting to compare Mark 16:17 in the different Bible translations. The Tyndale Bible of 1526 clearly links the casting out of devils with speaking with new tongues, which could be important.

"this kind does not come out, except by fasting and prayer" (Mat 17:21; Lamsa Bible)

The Lamsa Bible and other Peshitta based Bible translations has fasting before prayer, which is very interesting. Provided "prayer", in Mat 17:21, is the activity that casts out the oppressing devils, it sure seems that the logical order is the one of having fasting come first.

The synthesis of the two above quoted Bible verses could then be that the right order is: 1. fasting; 2. speaking in tongues; 3. eviction of oppressing devils.

Fasting could refer to a mourning and a longing for a state of holiness.

Speaking in tongues could refer to the spiritual warfare of swinging the sword of the word of God, through a baptism of the Holy Spirit, with the resulting

Eviction of oppressing devils.

  • I have always wondered why certain individuals get booted out from churches? Why can't the leaders just drive out the demons that are within these guys? Commented Jan 10, 2021 at 5:40
  • Not everyone who sins is demon possessed...
    – curiousdannii
    Commented Jan 11, 2021 at 6:22
  • @curiousdannii. Oppressing spirits can also be within a person, although in lesser control then what possessing spirits would be. Right? Commented Jan 12, 2021 at 0:06
  • I don't know, I don't have much thoughts about demons. But I do know that the main cause of sin is internal to a person. We sin because we are sinners, not because of anyone else. We are fully culpable. And so most cases of church discipline will have nothing to do with demons or exorcisms.
    – curiousdannii
    Commented Jan 12, 2021 at 0:09
  • What came first; the demon or the sin? Commented Feb 4, 2021 at 23:44

1 Be very careful 2 Don't think the spirit world is some joke 3. Pray everyday all day , 4.confess constantly 5 pray God help us give to others what we ask from Him 6. The olive oil , the oil of the people, James 5 part of healing, so important God sent the angel back in the garden to give it to Adam & Eve , 2 of God's names in Hebrew, spiritually the Name of God, strong protection healing in times of low faith 7. Do not be calling out the unsaved deads names.. you call them they come 8. All around us, i read where shamans have described smoking certain herbs in South America and can see them all around .. shadows, hatman, lady of the night, night hag of isa 34 9. We are stronger than them by God who is our strength, we personally can't do squat,, its all God 10 who is gonna put their hand on His and stop Him from what we ask through faith and belief

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    – agarza
    Commented Feb 24, 2021 at 13:46

Many great answers here. This book, A Hunger for God, by John Piper is highly recommended. May it lead you to understand how God loves you and cares for you.


  • Welcome to Bible Hermeneutics SE and thank you for your contribution. When you get a chance, please take the tour to understand how the site works and how it is different than others.
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    Commented Apr 19, 2021 at 4:04
  • Please reference the scriptures in your answers. This is an hermeneutic site. In any case, the linked article does not answer the above question.
    – Nigel J
    Commented Apr 19, 2021 at 6:14
  • @NigelJ, the author of the question would do well to re-read the scripture he quoted. Jesus is clearly telling the disciples that they failed because they are 'faithless and perverse'. He saw the condition of their hearts. Fasting and prayer are just a means of bringing out and expressing this very deep faith in God. The article I linked to conveys this. I recommend the book to the author of the question because he would do well to read thoroughly around the topic and understand the Bible from that perspective. This way, he can learn how to ask questions that are spiritually more discerned.
    – lilayoung
    Commented Apr 19, 2021 at 17:44
  • The community has up-voted the question significantly and many have attempted an answer. Your own response is not in keeping with the site and with the question. Please see the Tour and the Help as to the purpose and the functioning of the site.
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    Commented Apr 19, 2021 at 21:11
  • Thank you for explaining.
    – lilayoung
    Commented Apr 19, 2021 at 22:00