But they understood not that saying, and were afraid to ask him.
But they understood not that saying - "and it was hid from them, [so] that they perceived it not" (Luke 9:45),
And were afraid to ask him. Their most cherished ideas were so completely dashed by such announcements, that they were afraid of laying themselves open to rebuke by asking Him any questions. But "they were exceeding sorry" (Matthew 17:23). While the other Evangelists, as Webster and Wilkinson remark, notice their ignorance and their fear, Matthew, who was one of them, retains a vivid recollection of their sorrow. Remarks:
(1) When the keen-edged rebuke which our Lord administers to his apostles (Mark 9:19, and Matthew 17:17) is compared with the almost identical language of Yahweh Himself to His ancient people, on an occasion of the deepest provocation (Numbers 14:11; Numbers 14:27), who can help coming to the conclusion, that He regarded Himself as occupying the same position toward His disciples which the Lord God of Israel did toward His people of old? Let this be weighed. And it tends greatly to confirm this, that never once do we find anything approaching to a rebuke of them, or a correction of mistake in them or any others, for attributing too much to Him or conceiving of Him too loftily. Here, as everywhere else, it is the reverse. He takes with every charge of His "making Himself equal with God," and what He says in reply is but designed to make that good. Here, He is hurt at His disciples because their confidence in His power to aid them, even when at a distance from them, was not such as to enable them to grapple successfully even with one of the most desperate manifestations of diabolical power.
(2) Our Lord thinks such attachment to Him and confidence in Him as is found in all genuine disciples from the first, is not enough. As there are degrees in this-from the lowest to the highest, from the infancy to the manhood of faith-so He takes it ill when His people either make no progress, or inadequate progress; when, "for the time they ought to be teachers, they have need that one teach them" (Hebrews 5:12); when they do not "grow in grace, and in the knowledge of our Lord and Saviour Jesus Christ" (2 Peter 3:18).
(3) How often have we to remark that distress and extremity in honest hearts does more toward a right appreciation of the glory of Christ than all teaching without it! (See, for example, the notes at Luke 7:36-50; Luke 23:39-43.) Here is a man who, without any of the advantages of the Twelve, but out of the depths of his anguish, utters a speech more glorifying to Christ than all which they ever expressed during the days of His flesh-protesting his faith in the Lord Jesus, but in the same breath beseeching Him for help against his unbelief! To be conscious at once both of faith and of unbelief; to take the part of the one against the other; yet to feel the unbelief, though disowned and struggled against, to be strong and obstinate, while his faith was feeble and ready to be overpowered, and so to "cry out" even "with tears" for help against that cursed unbelief-this is such a wonderful speech, that, all things considered, the like of it is not to be found. The nearest to it is that prayer of the apostles to the Lord, "Increase our faith" (Luke 17:5). But besides that this was uttered by apostles, whose advantages were vastly greater than this man's, it was said a good while after the scene here recorded, and was evidently but an echo, or rather an adaptation of it. So that this man's cry may be said to have supplied the apostles themselves with a new idea, nay perhaps with a new view altogether of the power of Christ. And is it not true still, that "there are last which shall be first"?
(4) Signal triumphs in the kingdom of grace are not to be won by an easy faith, or by stationary, slothful, self-indulgent believers: they are to be achieved only by much nearness to God and denial of ourselves. As to "fasting," if the question be, Whether and how far is it an evangelical duty? there is a preliminary question, What is its proper object? Evidently the mortification of the flesh; and generally, the counteracting of all earthly, sensual, grovelling tendencies, which eat out the heart of our spirituality. Hence it follows, that whatever abstinence from food is observed without any reference to this object, and for its own sake, is nothing but "bodily exercise" (1 Timothy 4:8); and whatsoever abstinence is found by experience to have an exhausting, stupefying effect upon the spirit itself, is, so far as it is so, of the same nature. The true fasting is the opposite of "surfeiting" (Luke 21:34), which destroys all elasticity of spirit and all vigour of thought and feeling. And while Christians should habitually keep themselves far from this, by being sparing rather than otherwise in the satisfaction of their appetites, the lesson here taught us is that there are sometimes duties to be done and victories to be achieved, which demand even more than ordinary nearness to God in prayer, and more than ordinary denial of ourselves.