|Matthew Henry's Concise Commentary|
9:14-29 The father of the suffering youth reflected on the want of power in the disciples; but Christ will have him reckon the disappointment to the want of faith. Very much is promised to our believing. If thou canst believe, it is possible that thy hard heart may be softened, thy spiritual diseases may be cured; and, weak as thou art, thou mayest be able to hold out to the end. Those that complain of unbelief, must look up to Christ for grace to help them against it, and his grace will be sufficient for them. Whom Christ cures, he cures effectually. But Satan is unwilling to be driven from those that have been long his slaves, and, when he cannot deceive or destroy the sinner, he will cause him all the terror that he can. The disciples must not think to do their work always with the same ease; some services call for more than ordinary pains.
Gill's Exposition of the Entire Bible
And he said unto them,.... Matthew, besides the following reason, assigns another, as given by our Lord, why they could not cast out the foul spirit, which was their unbelief; of which they were guilty in some sort, as well as the Jews, and the father of the child; but Mark omits it, and only relates this as the reason;
this kind can come forth by nothing, but by prayer and fasting; which they had not observed; See Gill on Matthew 17:21.
Jamieson-Fausset-Brown Bible Commentary
29. And he said unto them, This kind can come forth by nothing but by prayer and fasting—that is, as nearly all good interpreters are agreed, "this kind of evil spirits cannot be expelled," or "so desperate a case of demoniacal possession cannot be cured, but by prayer and fasting." But since the Lord Himself says that His disciples could not fast while He was with them, perhaps this was designed, as Alford hints, for their after-guidance—unless we take it as but a definite way of expressing the general truth, that great and difficult duties require special preparation and self-denial. But the answer to their question, as given in Mt 17:20, 21 is fuller: "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" (Mt 17:20). See on Mr 11:23. "Howbeit this kind goeth not out but by prayer and fasting" (Mt 17:21), that is, though nothing is impossible to faith, yet such a height of faith as is requisite for such triumphs is not to be reached either in a moment or without effort—either with God in prayer or with ourselves in self-denying exercises. Luke (Lu 9:43) adds, "And they were all amazed at the mighty power of God"—"at the majesty" or "mightiness of God," in this last miracle, in the Transfiguration, &c.; or, at the divine grandeur of Christ rising upon them daily.
Second Explicit Announcement of His Approaching Death and Resurrection (Mr 9:30-32).
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