You were transfigured on the Mount, Christ God revealing Your glory to Your disciples, insofar as they could comprehend. Illuminate us sinners also with Your everlasting light, through the intercessions of the Theotokos. Giver of light, glory to You.
You were transfigured upon the mount, O Christ our God, and Your disciples, in so far as they could bear, beheld Your glory. Thus, when they see You crucified, they may understand Your voluntary passion, and proclaim to the world that You are truly the effulgence of the Father.
THE TRANSFIGURATION OF OUR LORD
Such are the marvels, truly worthy of God, celebrated in this present feast, which is an image and prefiguring of the future state of the righteous, whose splendour the Lord spoke of, saying: “Then shall the righteous shine forth as the sun” (Matt. 13:43). It is because of this that the Kontakion of this Feast is said daily (when there is not a great feast) in the Service of the Typica in perpetual commemoration of the glory that will be the lot of the Saints. According to tradition, the Lord’s Transfiguration came to pass forty days before His Crucifixion; this is why the Transfiguration is celebrated forty days before the Exaltation of the Cross.”
(taken from: http://goarch.org/chapel/saints)