Transfiguration

It is worth considering that of the three prophets assumed by God in the Old Testament, two of them appeared with the glorified Christ on Mount Tabor: Moses, giver of the Law, and Elias, who slew false prophets on Mount Carmel. The message God entrusted to both of them was that God demanded due reverence in worship and deportment from His people. The message of Christ, more difficultly, was that God asked something proactive of mankind, to love God with all one's heart and one's neighbor as one's self. 

Christ's Transfiguration displayed His albescent divinity, what St. Gregory Palamas called the "uncreated divine energies" (today that phraseology would be dangerously New Age). Perhaps we should recall that His divine also illuminated our humanity....

"For we have not by following artificial fables, made known to you the power, and presence of our Lord Jesus Christ; but we were eyewitnesses of his greatness. For he received from God the Father, honour and glory: this voice coming down to him from the excellent glory: This is my beloved Son, in whom I am well pleased; hear ye him." (2Peter 1:16-17, first nocturne of Mattins)

"Of this metamorphosis the chief work was to remove from the hearts of the disciples the stumbling at the Cross. Before their eyes was unveiled the splendour of His hidden majesty, that the lowliness of His freely-chosen suffering might not confound their faith. But none the less was there here laid by the Providence of God a solid foundation for the hope of the Holy Church, whereby the whole body of Christ should know with what a change it is yet to be honoured. The members of that body whose Head hath already been transfigured in light may promise themselves a share in His glory." (Pope St. Leo the Great, second nocturne of Mattins) 

Transfiguration: Paving the Way of the Cross

source: toledofavs.com

The modern trend with regards to the Transfiguration of our Redeemer is to emphasize His glory and divinity, which he revealed to Elias, Moses, Peter, James, and John. The Hesychast theology following the tradition of Palamas even extends this to include the manifestation of the uncreated, uncaused Divine energy of God. The ancient view is both simpler and more intuitive than either of these when we read the Gospel as a whole. From the Fathers in today's Mattins:

"The Lord takes chosen witnesses, and in their presence, reveals His glory. That form of body which He had in common with other men, He so transfigured with light, that His Face did shine as the sun, and His raiment became exceeding white as snow. Of this metamorphosis the chief work was to remove from the hearts of the disciples the stumbling at the Cross. Before their eyes was unveiled the splendour of His hidden majesty, that the lowliness of His freely-chosen suffering might not confound their faith. But none the less was there here laid by the Providence of God a solid foundation for the hope of the Holy Church, whereby the whole body of Christ should know with what a change it is yet to be honoured. The members of that body whose Head hath already been transfigured in light may promise themselves a share in His glory." Sermon of St. Leo the Great on the Transfiguration, taken from the second nocturne

"Since the Lord had spoken much concerning dangers, much concerning His Own sufferings, much concerning death, and the killing of His disciples, and had laid upon them many hard and grievous things, and since all these were in this present life, and already hanging over them, whereas the good things were matter for hope and waiting as, for example, that whosoever should lose his life for His sake should find it, for that the Son of Man should come in the glory of His Father, and reward every man according to his works. Therefore, to assure them by their own eyes, and show them what the glory is wherein He will come, He manifested and unveiled it to them, as far as in this life they were able to grasp it, lest they and especially Peter should grieve over their own deaths, or the death of their Lord." 57th Sermon on Matthew by St. John Chrysostom, taken from the third nocturne

As an addendum, I would like to point out one of my favorite features of the icon of the Transfiguration. something that has always amused me. The three Apostles are blinded by the light and unable to see. John and James are looking away, overpowered by the radiance of the Lord's illuminated majesty. Peter, however, has to say something. Indeed, Peter always has to say something. Throughout the four Gospels he relentlessly speaks up at inopportune times and gets himself in trouble. After receiving the keys to the Kingdom of Heaven he passes on his chance to be quiet and earns the Lord's sharp condemnation "Get behind Me, Satan." There may be some theological significance to Peter's orientation toward the Lord in the icon—he did suggest the erection of three tabernacles—yet I cannot help but think there was an element of humor on the iconographers' part in having Peter attempt to get the Lord's attention while more important things transpire.

Vigil of the Epiphany of Our Lord

From the Second Sermon on the Epiphany by St. Leo the Great:

Dearly beloved brethren, rejoice in the Lord; again I say, rejoice. But a few days are past since the solemnity of Christ's Birth, and now the glorious light of His Manifestation is breaking upon us. On that day the Virgin brought Him forth, and on this the world knew Him. The Word made Flesh was pleased to reveal Himself by degrees to those for whom He had come. When Jesus was born He was manifested indeed to the believing, but hidden from His enemies. Already indeed the heavens declared the glory of God, and their sound went out into all lands, when the Herald Angels appeared to tell to the shepherds the glad tidings of a Saviour's Birth; and now the guiding star leadeth the wise men to worship Him, that from the rising of the sun to the going down thereof, the Birth of the true King may be known abroad; that through those wise men the kingdoms of the east might learn the great truth, and the Roman empire remain no more in darkness.

The very cruelty of Herod, when he strove to crush at His birth this King Whom he alone feared, was made a blind means to carry out this dispensation of mercy. While the tyrant with horrid guilt sought to slay the little Child he did not know, amid an indiscriminate slaughter of innocents, his infamous act served to spread wider abroad the heaven-told news of the Birth of the Lord. Thus were these glad tidings loudly proclaimed, both by the novelty of their story, and the iniquity of their enemies. Then was the Saviour borne into Egypt, that nation, of a long time hardened in idolatry, might by the mysterious virtue which went out of Him, even when His presence was unknown, be prepared for the saving light so soon to dawn on them, and might receive the Truth as a wanderer even before they had banished falsehood.

Dearly beloved brethren, we recognise in the wise men who came to worship Christ, the first-fruits of that dispensation to the Gentiles wherein we also are called and enlightened. Let us then keep this Feast with grateful hearts, in thanksgiving for our blessed hope, whereof it doth commemorate the dawn. From that worship paid to the new-born Christ is to be dated the entry of us Gentiles upon our heirship of God and co-heirship with Christ. Since that joyful day the Scriptures which testify of Christ have lain open for us as well as for the Jews. Yea, their blindness rejected that Truth, Which, since that day, hath shed Its bright beams upon all nations. Let all observance, then, be paid to this most sacred day, whereon the Author of our salvation was made manifest, and as the wise men fell down and worshipped Him in the manger, so let us fall down and worship Him enthroned Almighty in heaven. As they also opened their treasures and presented unto Him mystic and symbolic gifts, so let us strive to open our hearts to Him, and offer Him from thence some worthy offering.