Jesus leads them up into a high mountain, and there is transfigured before them: "His face did shine as the sun, and his raiment was white as the light." Moses and Elias appeared also, talking with Him. I leave the subject of their discourse, which is deeply interesting, till we come to the Gospel of Luke, who adds a few other circumstances, which, in some respects, give another aspect to this scene.
Here the Lord appears in glory, and Moses and Elias with Him: the one the legislator of the Jews; the other (almost equally distinguished) the prophet who sought to bring back the ten apostate tribes to the worship of Jehovah, and who, despairing of the people, went back to Horeb, whence the law was given, and afterwards was taken up to heaven without passing through death.
These two persons, pre-eminently illustrious in the dealings of God with Israel, as the founder and the restorer of the people in connection with the law, appear in company with Jesus. Peter (struck with this apparition, rejoicing to see his Master associated with these pillars of the Jewish system, with such eminent servants of God, ignorant of the glory of the Son of man, and forgetting the revelation of the glory of His Person as the Son of God) desires to make three tabernacles, and to place the three on the same level as oracles. But the glory of God manifests itself; that is to say, the sign known in Israel as the abode (shechinah) of that glory;  and the voice of the Father is heard. Grace may put Moses and Elias in the same glory as that of the Son of God, and associate them with Him; but if the folly of man, in his ignorance, would place them together as having in themselves equal authority over the heart of the believer, the Father must at once vindicate the rights of His Son. Not a moment elapses before the Father's voice proclaims the glory of the Person of His Son, His relation to Himself, that He is the object of His entire affection, in whom is all His delight. It is He whom the disciples are to hear. Moses and Elias have disappeared. Christ is there alone, as the One to be glorified, the One to teach those who hear the Father's voice. The Father Himself distinguishes Him, presents Him to the notice of the disciples, not as being worthy of their love, but as the object of His own delight. In Jesus He was Himself well pleased. Thus the Father's affections are presented as ruling ours-setting before us one common object. What a position for poor creatures like us! What grace! 
At the same time the law, and all idea of the restoration of the law under the old covenant, were passed away; and Jesus, glorified as Son of man, and Son of the living God, remains the sole dispenser of the knowledge and the mind of God. The disciples fall on their faces, sore afraid, on hearing the voice of God. Jesus, to whom this glory and this voice were natural, encourages them, as He always did when on earth, saying, "Be not afraid." Being with Him who was the object of the Father's love, why should they fear? Their best Friend was the manifestation of God on the earth; the glory belonged to Him. Moses and Elias had disappeared, and the glory also, which the disciples were not yet able to bear; Jesus-who had been thus manifested to them in the glory given Him, and in the rights of His glorious Person, in His relations with the Father-Jesus remains the same to them as they had ever known Him. But this glory was not to be the subject of their testimony until He, the Son of man, was risen from the dead-the suffering Son of man. The great proof should then be given, that He was the Son of God with power. Testimony thereunto should be rendered, and He would ascend personally into that glory which had just shone forth before their eyes.
But a difficulty arises in the minds of the disciples caused by the doctrine of the scribes with regard to Elias. These had said that Elias must come before the manifestation of the Messiah; and in fact the prophecy of Malachi authorised this expectation. Why then, ask they, say the scribes that Elias must first come? (that is to say, before the manifestation of the Messiah); whereas we have now seen that Thou art He, without the coming of Elias. Jesus confirms the words of the prophecy, adding, that Elias should restore all things. "But," continues the Lord, "I say unto you, that he is come already, and they have done unto him whatsoever they listed; likewise shall also the Son of man suffer of them." Then understood they that He spoke of John the Baptist, who came in the spirit and power of Elias, as the Holy Ghost had declared by Zacharias his father.
Let us say a few words on this passage. First of all, when the Lord says, "Elias truly cometh first, and shall restore all things," He does but confirm that which the scribes had spoken, according to Malachi's prophecy, as though He had said, "They are in the right." He then declares the effect of the coming of Elias: "He shall restore all things." But the Son of man was yet to come. Jesus had said to His disciples, "Ye shall not have gone over the cities of Israel till the Son of man be come." Nevertheless He had come, and was even now speaking with them. But this coming of the Son of man of which He spoke, is His coming in glory, when He shall be manifested as the Son of man in judgment according to Daniel 7. It was thus that all which had been said to the Jews should be accomplished; and in Matthew's Gospel He speaks to them in connection with this expectation. Nevertheless it was needful that Jesus should be presented to the nation and should suffer. It was needful that the nation should be tested by the presentation of the Messiah according to the promise. This was done, and as God had also foretold by the prophets, "He was rejected of men." Thus also John went before Him, according to Isaiah 40, as the voice in the wilderness, even in the spirit and power of Elias; he was rejected as the Son of man should also be. 
The Lord then, by these words, declares to His disciples, in connection with the scene they had just left, and with all this part of our Gospel, that the Son of man, as now presented to the Jews, was to be rejected. This same Son of man was to be manifested in glory, as they had seen for a moment on the Mount. Elias indeed was to come, as the scribes had said; but that John the Baptist had fulfilled that office in power for this presentation of the Son of man; which (the Jews being left, as was fitting, to their own responsibility) would only end in His rejection, and in the setting aside of the nation until the days in which God would begin again to connect Himself with His people, still dear to Him, whatever their condition might be. He would then restore all things (a glorious work, which He would accomplish by bringing again His Firstborn into the world). The expression "restore all things" refers here to the Jews, and is used morally. In Acts 3 it refers to the effect of the Son of man's own presence.
The temporary presence of the Son of man was the moment in which a work was accomplished on which eternal glory depends, in which God has been fully glorified, above and beyond all dispensation and in which God and so man has been revealed, a work of which even the outward glory of the Son of man is but the fruit, so far as that depends on His work, and not on His divine Person; a work in which morally He was perfectly glorified in perfectly glorifying God. Still, with respect to the promises made to the Jews, it was but the last step in the testing to which they were subjected by grace. God well knew that they would reject His Son; but He would not hold them as definitively guilty until they had really done it. Thus in His divine wisdom (while afterwards fulfilling His unchangeable promises) He presents Jesus to them-His Son, their Messiah. He gives them every necessary proof. He sends them John the Baptist in the spirit and power of Elias, as His forerunner. The Son of David is born at Bethlehem with all the signs that should have convinced them; but they were blinded by their pride and self-righteousness, and rejected it all. Nevertheless it became Jesus in grace to adapt Himself, as to His position, to the wretched condition of His people. Thus also, the Antitype of the David rejected in his day, He shared the affliction of His people. If the Gentiles oppressed them, their King must be associated with their distress, while giving every proof of what He was and seeking them in love. He rejected, all becomes pure grace. They have no longer a right to anything according to the promises, and are reduced to receive all from that grace, even as a poor Gentile would do. God will not fail in grace. Thus God has put them on the true footing of sinners, and will nevertheless fulfil His promises. This is the subject of Romans 11.
Now the Son of man who shall return will be this same Jesus who went away. The heavens will receive Him until the times of the restitution of all things of which the prophets have spoken. But he who was to be His forerunner in this temporary presence here could not be the same Elias. Accordingly John was conformed to the then manifestation of the Son of man, saving the difference that necessarily flowed from the Person of the Son of man, who could be but one, while that could not be the case with John the Baptist and Elias. But even as Jesus manifested all the power of the Messiah, all His rights to everything that belonged to that Messiah, without assuming as yet the outward glory, His time not being come John 7), so John fulfilled morally and in power the mission of Elias to prepare the way of the Lord before Him (according to the we character of His coming, as then accomplished), and answered literally to Isaiah 40, and even to Malachi 3, the only passages applied to him. This is the reason that John said hewas not Elias, and that the Lord said, "If ye can receive it, this is Elias which was for to come." Therefore also John never applied Malachi 4:5, 6 to himself; but he announces himself as fulfilling Isaiah 40:3-5, and this in each of the Gospels, whatever may be its particular character. 
But let us go on with our chapter. If the Lord takes up into the glory, He comes down into this world, even now in Spirit and in sympathy, and meets the crowd and Satan's power with which we have to do. While the Lord was on the Mount, a poor father had brought to the disciples his son who was a lunatic and possessed by a devil. Here is developed another character of man's unbelief, that even of the believer-inability to make use of the power which is, so to say, at his disposal in the Lord. Christ, Son of God, Messiah, Son of man, had overcome the enemy, had bound the strong man and had a right to cast him out. As man, the obedient One in spite of Satan's temptations, He had overcome him in the wilderness, and had thus a right as man to dispossess him of his dominion over a man as to this world; and this He did. In casting out devils and healing the sick, He delivered man from the power of the enemy. "God," said Peter, "anointed Jesus of Nazareth with the Holy Ghost and with power, and he went about doing good and healing all those that were oppressed by the devil." Now this power should have been used by the disciples, who ought to have known how to avail themselves by faith of that which Jesus had thus manifested on earth; but they were not able to do it. Yet what availed it to bring this power down here, if the disciples had not faith to use it? The power was there: man might profit by it for complete deliverance from all the oppression of the enemy; but he had not faith to do so-even believers had not. The presence of Christ on earth was useless, when even His own disciples knew not how to profit by it. There was more faith in the man that brought his child than in them, for felt want brought him to its remedy. All therefore come under the Lord's sentence, "O faithless and perverse generation!" He must leave them, and that which the glory had revealed above, unbelief shall realise below.
Observe here, that it is not evil in the world which puts an end to a particular intervention of God; on the contrary, it occasions the intervention in grace. It was on account of Satan's dominion over men that Christ came. He departs, because those who had received Him are incapable of using the power that He brought with Him, or that He bestows for their deliverance; they cannot profit by the very advantages then enjoyed. Faith was wanting. Nevertheless observe also this important and touching truth that, as long as such dispensation from God continues, Jesus does not fail to meet individual faith with blessing, even when His disciples cannot glorify Him by the exercise of faith. The same sentence that judges the unbelief of the disciples calls the distressed father to the enjoyment of the blessing. After all, to be able to avail ourselves of His power, we must be in communion with Him by the practical energy of faith.
He blesses then the poor father according to his need; and, full of patience, He resumes the course of instruction He was giving His disciples on the subject of His rejection and His resurrection as the Son of man. Loving the Lord, and unable to carry their ideas beyond the circumstances of the moment, they are troubled; and yet this was redemption, salvation, the glory of Christ.
Before however going farther, and teaching them that which became the disciples of a Master thus rejected and the position they were to occupy, He sets before them His divine glory, and their association with Him who had it, in the most touching manner, if they could but have understood it; and at the same time with perfect condescension and tenderness He places Himself with them, or rather He places them in the same place with Himself, as Son of the great King of the temple and of all the earth.
Those who collected the tribute-money for the service of the temple come and ask Peter if his Master does not pay it. Ever ready to put himself forward, forgetful of the glory he had seen, and the revelation made to him by the Father, Peter, coming down to the ordinary level of his own thoughts, anxious that his Master should be esteemed a good Jew and without consulting Him, replies that He does. The Lord anticipates Peter on his coming in, and shews him His divine knowledge of that which took place at a distance from Himself. At the same time, He speaks of Peter and Himself as both children of the King of the temple (Son of God still keeping in patient goodness His lowly place as a Jew), and both therefore free from the tribute. But they should not offend. He then commands creation, (for He can do all things, as He knows all things,) and causes a fish to bring precisely the sum required, coupling anew the name of Peter with His own. He had said, "Lest we offend them"; and now, "Give unto them for me and thee." Marvellous and divine condescension! He who is the searcher of hearts, and who disposes at will of the whole creation, the Son of the sovereign Lord of the temple, puts His poor disciples into this same relationship with His heavenly Father, with the God who was worshipped in that temple. He submits to the demands that would have been rightly made on strangers, but He places His disciples in all His own privileges as Son. We see very plainly the connection between this touching expression of divine grace and the subject of these chapters. It demonstrates all the significance of the change that was taking place.
It is interesting to remark that the first epistle of Peter is founded on Matthew 16, and the second on chapter 17, which we have just been considering.  In chapter 16 Peter taught of the Father, confessed the Lord to be the Son of the living God; and the Lord said that on this rock He would build His church, and that he who had the power of death should not prevail against it. Thus also Peter, in his first epistle, declares that they were born again unto a living hope by the resurrection of Jesus Christ from the dead. Now it is by this resurrection that the power of the life of the living God was manifested. Afterwards he calls Christ the living stone, in coming unto whom we, as living stones, are built up a holy temple to the Lord.
In his second epistle he recalls, in a peculiar manner, the glory of the transfiguration, as a proof of the coming and the kingdom of the Son of man. Accordingly he speaks in that epistle of the judgment of the Lord.