On the sixth of August, the Holy Church of God joyfully celebrates and commemorates the Holy Transfiguration of our Lord and God and Savior Jesus Christ. Since Christ had spoken to His Disciples of the many dangers that were to befall Him, including His passion and death, as well as the martyrdom of His Disciples, all the things that were at hand in the present life, and the promise of the good things to come; He wanted to reveal these things to them, and show them the glory with which He would come. And so He brought them up to Mount Tabor alone and transfigured before them. His face shined as the sun and His clothes became as white as the light, and Moses and Elijah were seen speaking with Him.
He took three Disciples aside with Him, as they were the greatest among the Apostles; Peter, because he loved Christ dearly, John, because he was the beloved disciple, and James, because he was able to drink the cup that the Lord drank. He brought Moses and Elijah to the center, correcting the inaccurate assumptions concerning Him by many. For some of the them were saying He was Elijah, and others Jeremiah. This is why He brought the Greatest of the Apostles with Him: so that they could see the Master and servant together, and so they might know, that He is the one that has all dominion over life and death.
(Μηναίον [Menaion], Synaxarist of August 6th)