Jesus said to them: Because of your unbelief. For, amen I say to you, if you have faith as a grain of mustard seed, you shall say to this mountain, Remove from hence hither, and it shall remove; and nothing shall be impossible to you.

“Or, all faith is likened to a grain of mustard-seed, because faith is looked on with contempt by men, and shews as something poor and mean; but when a seed of this kind lights upon a good heart as its soil, it becomes a great tree. The weakness of this lunatic’s faith is yet so great, and Christ is so strong to heal him amidst all his evils, that He likens it to a mountain which cannot be cast out but by the whole faith of him who desires to heal afflictions of this sort.”

“The disciples had received from the Lord the power over unclean spirits, and when they could not heal the dæmoniac thus brought to them, they seem to have had misgivings lest they had forfeited the grace once given to them; hence their question. And they ask it apart, not out of shame, but because of the unspeakable matter of which they were to ask. Jesus said unto them, Because of your unbelief.”

“And when he had come — here he foretells the tranquility of glory, which is assailed by the oppression of demons and the disturbance of men. And first he foretells that the first of these ceases through the curing of the lunatic; second, that the second ceases. And concerning the first, first the curing of the lunatic is set down; second he foretells the Passion, at "And while they abode in Galilee," etc.; third, concerning the payment of the tribute, at "And when they were come to Capernaum," etc. Concerning the first, first he heals; then he resolves the doubt, at "Jesus said to them," etc. Concerning the first he does two things. First the petition of the father is set down; second the granting of it, at "Bring him here to me." Concerning the first he does three things. For first the time is set down; second the indication of the sick one; third the petition. The time is set down when he says, "And when he was come to the multitude." Peter, enticed by the sweetness of glory, would always wish to be on the mountain; but Christ, out of the charity he had toward the crowds — because charity "seeketh not her own" — wished to come down from the mountain, so that the crowds might have access to him. Hence, when he had come, "there came to him a man falling down on his knees before him." If he had not come down, that man would not have come to him. And he approached humbly, because he fell on his knees, for "God hearkens to the prayer of the humble," Psalm 101:18. By this one the human race can be signified. Philippians 2:10: "that in the name of Jesus every knee should bow, of those in heaven, on earth, and under the earth," etc. Then the petition is set down. He does not ask, but sets forth the sickness; for it suffices to set forth one's misery to the merciful one. First he sets forth the sickness; second, its symptoms; third, that he could not find a remedy. He says therefore, "Lord, have mercy on my son, for he is a lunatic." It should be noted that many ask for themselves, as above concerning the woman having the flow of blood; sometimes someone asks on behalf of another, as here; but sometimes he cures someone who has not asked, as in spiritual sickness, as is found concerning the publican, Luke 18:12ff.; sometimes, however, someone is cured at the petition of another, as is found in James, last chapter, 16: "Pray for one another, that you may be saved"; sometimes without prayer, as in the conversion of Paul, Acts 9:4ff. But what is meant by saying that he is a lunatic? Properly speaking, a lunatic is one who is deranged according to the phase of the moon. But it seems that this one was not a lunatic but rather possessed by a demon, since below it is stated that "the demon went out from him." It can be said that this is not the word of the Evangelist, but of the deceived father, who believed him to be a lunatic. Or it is because above, at 4:24, it is stated that he cured lunatics, and these were possessed by demons. Some say, as do certain physicians, that they were not deranged by a demon but by an evil complexion, or disposition of the body, and this because, as the moon waxes, every moist thing increases. Thus, since the brain is most moist, when the moon suffers a defect, the brain itself also suffers a defect; and so such people suffer a failing when the moon is waning. But this is against the faith, because Scripture expressly calls them possessed by demons; and this is evident, because they speak from the spirit, since many who are ignorant suffer in this way, and yet they speak of the Scriptures. Therefore it must be said that evil spirits intend in many ways to lie in wait for men, and wish to defame them; therefore certain demons induce sicknesses and vexations according as they see an impression of the stars fitting for this, so as to lead men into error, so that they believe it happens to them that they suffer evil solely from the influence of the stars. "And he suffers grievously." Here the symptoms are set down. In any sickness there are different degrees; for some have a more severe fever, others a milder one; thus this one too was greatly afflicted. For "he often falls into the fire, and frequently into the water": therefore he was in great danger. Hence it must be noted that the Lord does not withdraw his hand in dangers. Hence he would already be dead, had God not stretched out his hand, as is read concerning Job 2:6: although Satan tormented him greatly, yet the Lord commanded him not to lay a hand upon his soul. By this one an unstable reason is signified, concerning which it is said in Ecclesiasticus 27:12: "A fool is changed as the moon." And he sometimes falls into the fire, namely of wrath; Deuteronomy 32:22: "A fire is kindled in my rage, and it shall burn even to the lowest hell." Frequently into the water, namely of desire. "Thou art poured out as water, thou shalt not grow," Genesis 49:4. "I offered him to thy disciples, and they could not cure him." Here the wickedness of this man is touched upon, since he wished to accuse the disciples; hence Ecclesiasticus 11:33: "who puts a stain upon the elect." Hence the Lord rebukes them: "And Jesus answering, said: O unbelieving and perverse generation." Hence the response is set down; and he does two things. First he rebukes the vice; second he confers the benefit. He says therefore, "And Jesus answering," etc. This man wished to defame the disciples before the crowds, and also Jesus, as though he did not have this power, and many were agreeing with him in this; therefore Christ inveighs against the whole nation, and charges them with unbelief, saying "unbelieving generation," because this was not on account of the powerlessness of the disciples, but on account of their unbelief. Likewise concerning perversity, and "perverse," because they imposed their own fault upon the apostles; Deuteronomy 32:5-6: "A depraved and perverse generation, is it thus that you repay the Lord, O foolish and unwise people?" "How long shall I be with you?" And Christ sets forth two things. First their impenitence; second the divine patience, because there is no fitting fellowship of the just with the unjust; Ecclesiasticus 13:21: "As the wolf hath fellowship with the lamb, so the sinner with the just"; 2 Corinthians 6:15: "What agreement hath Christ with Belial?" Hence he means to say: you enjoy my company, and yet you do not cease to detract from me and my disciples. And, as Jerome says, the Lord does not say this as one who is angry, but speaks in the manner of a physician who comes to a sick man who will not keep his precepts, and who says: How long shall I visit thee, who wilt not keep my commands? Therefore he gives an example to prelates, that although men oppose them, they should nonetheless confer benefits, just as he himself cured the son of this man who was detracting from him and his disciples. Hence he says, "Bring him hither to me." And first the manner of curing is set down; second the effect. First the agent is set down, namely Christ; hence he says, "Bring him to me." Men sin in many ways. Some from ignorance, some from weakness, some from malice. He who sins from ignorance can be instructed by a man; he who sins from weakness, namely he who sins through incontinence, who grieves over his sin, and is led along by his passions — this one cannot be healed by just anyone, but it is necessary that he be brought to Jesus, who heals all our infirmities. And this is the way, for "he rebuked him," because this had happened to him through his own sin; Proverbs 6:2: "Thou art ensnared by the words of thy mouth, and caught by thy own speech." Or "he rebuked him," namely the demon. The effect follows: "and the demon went out from him, and the boy was cured from that hour," because "he spoke, and they were made," Psalm 148:5. "Then the disciples came to Jesus secretly," etc. Above, the Lord cured the lunatic; here he answers the question of the disciples. And first the question is set down; second the response, at "Jesus said to them," etc. But that you may understand their petition, you should know that above, at 10:8, the Lord had given them the power of casting out demons; hence they doubted whether they had lost the grace given, on account of some fault; therefore they came to Jesus, etc. But why "secretly"? Not on account of shame, but because they were to hear something great, and secret things ought not to be told to all; above, chapter 13:11: "To you it is given to know the mysteries of the kingdom of heaven, but to them it is not given." "Jesus said to them." Here he responds. And first he answers their question; second he sets forth a general teaching, at "But this kind is not cast out but by prayer and fasting." Concerning the first, first he answers the question, and second he explains the answer, at "For amen I say to you," etc. They had asked, "Why could we not cast him out?" The Lord answers: "Because of your unbelief." Here it must be considered that before they had received the Holy Spirit in such fullness, with which they were all filled with the Holy Spirit, Acts 2:4, they suffered certain weaknesses; hence the Lord reproves them, Luke, last chapter, 25: "O foolish, and slow of heart to believe." Nor is it a wonder, because while the Lord was on the mountain, those who had been foremost in faith, namely Peter, James, and John, were absent: for weakness of faith is a cause of not working miracles, because the working of miracles is from omnipotence, since faith rests upon omnipotence; hence where there is weakness of faith, there is a failure of miracles. Hence it is stated above at 13:58 that in his own country Christ did not work but a few miracles, on account of their unbelief. Sometimes miracles happen on account of the urgent request of the one asking, as above at 15:22ff. is found concerning the Canaanite woman; sometimes to manifest the holiness of some saint: and this is found at 4 Kings 13:20-21, where it is said that when raiding bands of the Syrians had come into the land of Israel, they cast a dead body down beside Elisha, and it came back to life — not because the dead man had merited it, but for the manifestation of the holiness of Elisha. "For amen I say to you, if you have faith as a grain of mustard seed," etc. Here he explains his response. And a certain conditional is set down, whose antecedent is "if you shall have faith," etc., and whose consequent is "you shall say to this mountain, Remove, and it shall remove." Some say that faith compared to a grain of mustard seed is a small faith; as if he were saying: if you have some faith, you shall say, etc. But Jerome disproves this, because the Apostle says: "If I should have all faith, so that I could remove mountains." Hence a perfect faith is required for the removing of mountains. By this, that he says "as a grain of mustard seed," a threefold perfection of faith is designated. For we find in the grain fervor, fruitfulness, and smallness. Before the grain is crushed, it seems to have no heat; when it is crushed, it begins to grow hot: so a faithful man, before he is tested, seems contemptible; but when he is truly worn down, then his holiness appears. 1 Peter 1:7: "now for a little while, if need be, you are made sorrowful, that the trial of your faith may be found much more precious than gold, which is tried by fire." Likewise we find in the grain fruitfulness, above at chapter 13, that although it is small, it grows into a great crop, so that the birds of the air dwell there. Hebrews 2, where the works of faith are recounted, and it follows: "the saints through faith conquered kingdoms," etc. Likewise we find smallness, and by this the humility of faith can be designated. For then is someone recognized as humble in faith, when he acquiesces to the words of God; 1 Timothy 6:3: "if anyone does not acquiesce to the words of God, he is proud." Thus, on the contrary, he who acquiesces to the words is humble. He means to say, therefore: if you have faith — and if it is a fervent faith, unfailing, fruitful in works, and small and humble — you shall say to this mountain, "Remove," and it shall remove. Here is a question which unbelievers raise. It is not found that the apostles ever did this. Chrysostom answers: even if it is not found concerning the apostles, it is nevertheless found concerning apostolic men. For it is read in the book of Dialogues of blessed Gregory that when a certain man wished to build a church, and had no place to build it, he commanded a mountain to give way to him, and it gave way. Or perhaps they did do it, but it is not written. Or it can be said that if they did not do it, it was not on account of impossibility, but because the occasion did not present itself. Hence miracles were done sometimes for necessity, sometimes for usefulness; and because it was not necessary, therefore they did not do it. Or the mountain is put for the Devil. "Remove hence," that is, from this body, "and it shall remove." Or, according to Augustine, it is understood of the spirit of pride. "And nothing shall be impossible to you." And what does this mean? Will they be omnipotent? No, because he alone is truly omnipotent who can do all things by his own power; but they act not by their own power, but as a king commands in one way and a servant in another, because the king commands in his own name, the servant in the name of the king. "But this kind of demons" (the "this" here does not indicate only the kind of the lunatic, but every kind of demons) "is not cast out but by prayer and fasting." Chrysostom says that the more the soul is elevated, the more terrible it is to demons; for Christ himself is terrible to demons: hence those who are joined to Christ are terrible to it. But the elevation of the mind is hindered by the heaviness of the flesh, is hindered by surfeiting and drunkenness; hence in Luke 21:34: "Take heed lest your hearts be weighed down with surfeiting and drunkenness," etc. Hence he who is weighed down by drunkenness cannot have his mind toward God; therefore fasting is required for the elevation of the mind; hence in Tobit 12:8: "Prayer is good with fasting." Likewise Daniel 9:3: "I, Daniel, set my heart to pray in fasting." Therefore, as Origen says, in order that the spirit be expelled, one must not dwell upon feastings, but upon prayers and fastings. Or by the lunatic the instability of the flesh is designated: or the one who is led about by diverse desires. He who often falls into fire and water — such a one is not cured except by fasting and prayer. Galatians 5:17: "The flesh lusteth against the spirit, and the spirit against the flesh." It is necessary, therefore, that you weaken the flesh and strengthen the spirit. But the spirit is strengthened through prayer, because prayer is the ascent of the mind to God; while the flesh is weakened through fasting. Or, because the spirit does not cease its struggle against the flesh, therefore, that such a battle may cease, good operations are required, which are signified by prayer, and abstinence from evil, which is signified by fasting. "And while they abode in Galilee," etc. Above, the tranquility of glory was figured through liberation from the power of demons; this liberation was accomplished through the death of Christ; Hebrews 2:14: "that through death he might destroy him who had the empire of death," that is, the Devil, "and might deliver them, who through the fear of death were all their lifetime subject to servitude." Therefore he immediately adds concerning the foretelling of the Passion. And first the foretelling is set down; second the effect, at "and they were exceedingly sorrowful." Our Lord had foretold his Passion before, and now also, and in what follows. And why so many times? Because things which are foreseen disturb less; therefore, because it was going to happen that the disciples would be scandalized at the death of the Lord, he wished to foretell it to them often, so that they would be less scandalized. But he always adds something. Before he touched upon the killing, but not upon the betrayal; but here he touches upon the betrayal, saying, "the Son of man shall be betrayed." And rightly does he say "Son of man," because although he who is betrayed is the Lord of glory, yet it is according as he is Son of man that he is betrayed. Hence Augustine: although certain things are said of the Son of God and of the Son of man, yet a distinction is made, because weak things are said of the human nature, stable things of the divine nature. But he does not say by whom he was betrayed. For he handed himself over; Galatians 2:20: "who delivered himself for me." He was handed over by the Father, "who spared not his own son, but delivered him up for us all," Romans 8:32. Likewise he was betrayed by Judas; above, 10:4: "who also betrayed him." Likewise by demons: John 13, it is stated that the Devil put it into the heart of Judas that he should betray him. And Wisdom 2:12: "Come, let us kill the just one." "And the third day he shall rise again." Hosea 6:3: "He will revive us after two days: on the third day he will raise us up, and we shall live in his sight." The effect follows: "and they were made sorrowful." They attended to both the death and the resurrection, but they did not see the benefit of it. John 16:6: "because I have spoken these things to you, sorrow hath filled your heart." "And when they were come to Capernaum." Having completed the treatment of the tranquility of glory, he sets down the payment of the tribute; Isaiah 14:4: "the tribute hath ceased"; Job 3:19: "the servant is free from his master." Hence he does three things. First he sets down the exacting of the tribute; second the freedom of the sons; third the paying of the tribute. He says, "And when they were come," etc. A didrachma is called a double drachma. Hence every Jew owed a double drachma each year. But whence did this tribute come? Some say it was from the law, Exodus 13, that because the Lord had slain the firstborn of Egypt, therefore he decreed that all the firstborn should be his, and that the sons should be redeemed. Afterward he commanded that the Levites be prepared for this service. And afterward he ordered that the Levites be numbered. And there were found more firstborn than Levites. Then he commanded that a price be paid for redemption. Jerome says that it was not from the law of God, but of the emperor: Judea had recently become tributary to the Romans, so that it should pay a poll-tax per head. And this seems truer, because below it is said: "The kings of the earth, of whom do they receive tribute?" Therefore he is speaking of the imperial tribute. But why in Capernaum? Because it was received from each person in his own city, and Capernaum was the principal city of Galilee. But because they held Christ in reverence, therefore they do not approach him, but Peter; and they asked only with gentleness: "Doth not your master pay the didrachma?" Then Peter's response is set down, and he says, "Yes"; that is, it is true that he does not pay it. Chrysostom says that, lest he be disturbed, he said "yes," meaning he pays. There follows Christ's question, then Peter's response. In the question two things are to be considered: namely, that he was not terrified by the disclosure of it, because, since he was in such a state, he was held to a certain unworthiness; and some are so disposed that, when they see some weakness in a great person, they are immediately scandalized. Therefore, lest they be scandalized, he forestalls this; therefore alongside the weakness he set forth something great, namely, that though absent he knew what had been said to Peter. "All things are naked and open to his eyes," Hebrews 4:13. Likewise it should be noted that he commits the judgment to Peter, for he spoke to him more often, saying, "What thinkest thou, Simon?" Job 12:11: "Doth not the ear discern words?" "The kings of the earth, of whom do they receive tribute, or custom?" There is a difference between tribute and custom: for tribute is levied on fields and vineyards, whereas the custom is given per head. Hence, in sign of his subjection, a subject man owes something; and this is called the custom. From this he wishes to argue that, since the sons of kings do not pay tribute, he himself is not bound to pay: for he is the king of kings, through whom all reign. Likewise, according to the flesh, he was of the royal seed. "Who was made of the seed of David according to the flesh," Romans 1:3. Chrysostom says that from this we can consider that he is a natural son, because it is said first concerning him who is a natural son. But he said: "From strangers." Then Christ's response is set down, that kings spare their own sons. Isaiah 3:15: "Why do you crush my people, and grind the faces of the poor?" For it seems just. For he who presides ought to have care for his subjects; therefore his subjects ought to serve him as members serve the body. For just as the members of the body serve the whole body out of what is proper to them, so every subject ought to serve the community out of his own goods. Therefore the Lord concludes, "Then the children are free." Origen: in one way, thus. Therefore the sons of the kings of the earth are free, but the sons of God are free with God. But what does this contribute to the point at hand? Either he speaks of sons according to the flesh, and in that case he himself was not a son according to the flesh; or according to the spirit, and then all Christians would be free. But this is against the Apostle: "Render to all men their dues... to whom tribute is due, tribute." I say that this held true concerning him who was a son by nature. For he was truly free. But those who are free according to the spirit have their freedom in the same way as their sonship, through conformity to Christ, who is "the firstborn amongst many brethren," Romans 8:29. Insofar as they are conformed to the firstborn, they are free. Philippians 3:21: "who will reform the body of our lowness, configured to the body of his glory." "But that we may not scandalize them," etc. It is true that the Lord is free, but because he took the form of a servant, as is found in Philippians 2, therefore he did not refuse to pay, and in this he gave an example of humility. And in this payment three things worthy of praise and of admiration are noted. First, his gentleness, for he himself is meek, according as he himself testifies above at 11:29: "Learn of me, because I am meek and humble of heart." He is properly called meek who wishes to offend no one; 1 Corinthians 10:32: "Be without offense to the Jews, and to the Gentiles, and to the Church of God." But against this an objection is raised. Above at 15:12 it is found that the disciples said, "Lord, dost thou know that they are scandalized at this word?" And the Lord said, "Let them alone; they are blind, and leaders of the blind." He did not then take care about the scandal, but here he does take care. Hence it must be said that scandal sometimes arises from truth; and then it is not to be attended to; sometimes from weakness or ignorance; and this kind is to be attended to. But if he had not paid, their scandal would have arisen from ignorance, because they did not know God. Likewise the poverty of Christ is to be admired, for he was so poor that he had nothing with which to pay; 2 Corinthians 8:9: "who, though he was rich, became poor, that through his poverty you might be rich." Someone can object: did he not have a money-bag? It is true, but everything in it was given over for the use of the poor. He considered it a plundering to spend on other uses what was for the use of the poor. Chrysostom says that he paid it, so that, while paying the tribute, on the one hand he might show his power, and on the other a mystery. "Go to the sea, and cast a hook, and that fish which shall first come up, take; and when its mouth is opened, thou shalt find a stater." In that stater there was the image of Caesar: and it signifies the Devil, who had nothing in him; John 14:30: "The prince of this world cometh, and in me he hath not any thing." Therefore, because he had nothing of his own in him, therefore he did not wish to pay out of his own. Likewise his providence; therefore he says that we ought to marvel how he could know that a fish would immediately come along which would have a stater in its mouth. But if it was not already there, but he created it anew, it is to be marveled at; but if he led it to the hook, it was a mark of great providence. By this fish which first came to the hook, the first martyr, blessed Stephen, is understood, who had in his mouth a stater which was worth a didrachma, and double; and it signifies Stephen himself, who saw both the divinity and the humanity. Or it can be understood to signify Adam. Likewise note, that if someone speaks often of riches and of money, he has a stater in his mouth; hence whoever converts such a person receives a fish that has a stater in its mouth. Likewise humility is signified: hence, "taking that, give it to them for me and for thee." And in this, that the tribute was paid for Peter and for himself, it is signified that through the Passion of Christ, he acquired for himself the glory of the resurrection; Philippians 2:9: "For which cause God also hath exalted him." Peter and the others were redeemed from penalty and guilt. Or otherwise: because he suffered for himself, that he might acquire for his body the glory of the resurrection; for the people, that he might wash them from their sins. "For he washed us from our sins in his own blood."”

“Then came the disciples to Jesus apart,.... Or "secretly", as the Vulgate Latin, and Munster's Hebrew Gospel read; that is, privately, and when alone; and as Mark says, "when he was come into the house"; and was by himself, then came the nine disciples to him, to converse with him about this matter, and said unto him, why could not we cast him out? That is, the devil, and so cure the lunatic; the Syriac and Persic versions render it, "why could not we heal him?" The lunatic; which only could be done by casting out the demon: they were concerned, fearing they had lost the power which Christ had bestowed on them, and wanted to know what they had done, which had deprived them of it; and what should be the cause of their late unsuccessful attempt, when they had so frequently triumphed over the unclean spirits, that were subject to them. Though they might have learned from the answer Christ gave to the father of the lunatic, and the general character of the Jewish nations in that answer, the true reason of their own inability; but this they took no notice of, imagining it belonged entirely to others, and not to them.”

“If you have faith as a grain of mustard-seed. Christ insinuates to his apostles, as if they had not yet faith enough to work great miracles, which require a firm faith joined with a lively confidence in God. The mustard-seed is brought in with an allusion to its hot and active qualities. (Witham) — That is, a perfect faith; which, in its properties and its fruits, resembles the grain of mustard-seed in the parable. (Chap. xii.[xiii.?] 31.) (Challoner) — By faith is here understood, not that virtue by which we assent to all things that are to be believed of Christ, the first, of the theological virtues, in which the apostles were not deficient, but that confidence in the power and goodness of God, that he will on such an occasion exert these, his attributes, in favour of the supplicant. To have a true faith of this kind, and free from all presumption, is a great and high privilege, which the Holy Ghost breathes into such only as he pleases. (Jansenius) — Examples of this efficacious faith are given by St. Paul. (Hebrews chap. ii.[xi.?]) St. Gregory of Neo-Cęsarea is also related, by Eusebius and Ven. Bede, to have removed by the efficacy of his faith a rock, which obstructed the building of a church; thus literally fulfilling the promise of Jesus Christ. (Tirinus) — The faith of the apostles, especially of those that had not been present at the transfiguration, was not perfect and complete in all its parts, till after the resurrection and ascension of Jesus Christ, and the descent of the Holy Ghost. (Haydock) — St. Jerome understands by mountains, things the most difficult to be effected.”