(21) This kind goeth not out but by prayer and fasting.--The words imply degrees in the intensity of the forms of evil ascribed to demons amounting to a generic difference. Some might yield before the energy of a human will, and the power of the divine Name, and the prayers even of a weak faith. Some, like that which comes before us here, required a greater intensity of the spiritual life, to be gained by the "prayer and fasting" of which our Lord speaks. The circumstances of the case render it probable that our Lord himself had vouchsafed to fulfil both the conditions. The disciples, we know, did not as yet fast (Matthew 9:14-15), and the facts imply that they had been weak and remiss in prayer. The words are noticeable as testifying to the real ground and motive for "fasting," and to the gain for the higher life to be obtained, when it was accompanied by true prayer, by this act of conquest over the lower nature. So St. Peter's vision (Acts 10:9-10), and the appointment of Paul and Barnabas by the direct guidance of the Spirit (Acts 13:2), are both connected with fasting. And St. Paul, besides the "hunger and thirst" that came upon him as the incidents of his mission-work, speaks of himself as "in fastings often" (2Corinthians 11:27).

Verse 21. - This verse is omitted in many good manuscripts and by the Revised Version, it being considered to have been introduced from the parallel passage of St. Mark. It gives the second reason for the failure of the nine. This kind... fasting. Though all things are possible to faith, some works are more difficult of accomplishment than others. This kind can mean only this kind of evil spirit, or demons generally. But the latter interpretation is excluded by the fact that the apostles had already exercised successfully their power over devils without special prayer or fasting. The words point to a truth in the spiritual world, that there are different degrees in the Satanic hierarchy (comp. Matthew 12:45); some demons are more malignant than others, and have greater power over the souls of men. In the present case the possession was of long standing; it revolved a terrible bodily malady; it was of an intense and unusual character. The mere word of exorcism, or the name of Jesus, spoken with little spiritual faith, could net overcome the mighty enemy. The exorcist needed special preparation; he must inspire and augment his faith by prayer and self-discipline. Prayer invokes the aid of God, and puts one's self unreservedly in his hands; fasting subdues the flesh, arouses the soul's energies, brings into exercise the higher parts of man's nature. Thus equipped, a man is open to receive power from on high, and can quell the assaults of the evil one.

17:14-21 The case of afflicted children should be presented to God by faithful and fervent prayer. Christ cured the child. Though the people were perverse, and Christ was provoked, yet care was taken of the child. When all other helps and succours fail, we are welcome to Christ, may trust in him, and in his power and goodness. See here an emblem of Christ's undertaking as our Redeemer. It encourages parents to bring children to Christ, whose souls are under Satan's power; he is able to heal them, and as willing as he is able. Not only bring them to Christ by prayer, but bring them to the word of Christ; to means by which Satan's strong-holds in the soul are beaten down. It is good for us to distrust ourselves and our own strength; but it is displeasing to Christ when we distrust any power derived from him, or granted by him. There was also something in the malady which rendered the cure difficult. The extraordinary power of Satan must not discourage our faith, but quicken us to more earnestness in praying to God for the increase of it. Do we wonder to see Satan's bodily possession of this young man from a child, when we see his spiritual possession of every son of Adam from the fall!Howbeit, this kind goeth not out,.... The Vulgate Latin renders it, "is not cast out"; and so do the Arabic version, and Munster's Hebrew Gospel; and which confirm the more commonly received sense of these words, that they are to be understood of that kind of devils, one of which was cast out of the lunatic, and was of the worst sort, of a fierce and obstinate kind; and having had long possession, was not easily ejected: and that there is a difference in devils, some are worse and more wicked than others, is clear from Matthew 12:45 and not of that kind of miracles, or kind of faith to the working of such miracles. Moreover, the above versions, as they fitly express the word here used; see Mark 9:17 compared with Matthew 15:17. So they pertinently set forth the dispossession of devils, who do not go out voluntarily, but by force; and this sort could not be ejected,

but by fasting and prayer: that is, in the exercise of a miraculous faith, expressed in solemn prayer to God, joined with fasting. It seems that Christ not only suggests, that faith was greatly wanting in his disciples; for which reason they could not cast out the devil, and heal the lunatic; but they had been wanting in prayer to God, to assist them in the exercise of their miraculous gifts; and that whilst Christ, and the other three disciples were on the mount, they had been feasting and indulging themselves with the people, and so were in a very undue disposition of mind, for such extraordinary service, for which our Lord tacitly rebukes them. This agrees with the notions of the Jews, who think that, by fasting, a divine soul (f) , "may obtain that which is sought for"; and that among other things, for which a private person may afflict himself with fasting, this is one, , "because of an evil spirit" (g); which they think may be got rid of this way.

(f) Jacchiades in Dan. x. 3.((g) T. Bab. Taanith, fol. 22. 2. Maimon. Hilch. Taaniot, c. 1. sect. 6.