The Celebration of the Transfiguration of Our Lord Jesus began in the eastern church in the late fourth century. It is celebrated on August 6th the same day of the dedication of the first church on the Mount Tabor, traditionally called the “high mountain”. The western church did not take to this celebration until the late ninth century and was declared a universal feast by Pope Callistus III in 1457.
The transfiguration is recorded in the Gospel books of Matthew 17:1-8; Mark 9:2-8 and in Luke 9:28-36. It is the feast that celebrates Jesus' radical change of appearance while in the presence of Peter, James, and John, on a high mountain. The transfiguration precedes the crucifixion, resurrection and ascension of Christ. Maybe this was a way in preparing, strengthening and comforting the disciples for the difficult times that lie ahead.
As told in Matthew 17:1-8 (NIV)
1 “After six days Jesus took with him Peter, James and John the brother of James, and led them up a high mountain by themselves.2 There he was transfigured before them. His face shone like the sun, and his clothes became as white as the light. 3 Just then there appeared before them Moses and Elijah, talking with Jesus. 4 Peter said to Jesus, “Lord, it is good for us to be here. If you wish, I will put up three shelters—one for you, one for Moses and one for Elijah.” 5 While he was still speaking, a bright cloud covered them, and a voice from the cloud said, “This is my Son, whom I love; with him I am well pleased. Listen to him!” 6 When the disciples heard this, they fell face down to the ground, terrified. 7 But Jesus came and touched them. “Get up,” he said. “Don’t be afraid.” 8 When they looked up, they saw no one except Jesus.”
Transfiguration provides one of the most distinctive and dramatic showings of Jesus' divinity. Many consider the transfiguration as a “unique miracle” as it happens to Jesus himself and is one of the five milestones in the gospel narrative of the life of Jesus; baptism, crucifixion, resurrection and ascension being the others.
The transfiguration happening on the “high mountain” has much significance for believers. Christian theologians believe this: “the Transfiguration is a pivotal moment, and the setting on the mountain is presented as the point where human nature meets God: the meeting place for the temporal and the eternal, with Jesus himself as the connecting point, acting as the bridge between heaven and earth.” (Lee, Dorothy (2004). Transfiguration. Bloomsbury Academic.)
It's also truly a testament of Jesus being the messenger and mouthpiece of God. Matthew 17:5 “...This is my Son, whom I love; with him I am well pleased. Listen to him!”
The scriptures also teach us that through the transfiguration, God assigns Jesus a special honor and glory, and God exalts Jesus and appoints him as the ruler and judge. Echoing the teaching by Jesus as in Matthew 22:32 that God is not "the God of the dead, but of the living;” the transfiguration; with the showing of Elijah and Moses reaffirms that they live in the presence of the Son of God. That those that have faith have life after death with our God.
The Greek word for transfigured is "metamorpho" and it means to transform, literally or figuratively to metamorphose, or to change. So through Jesus’ transfiguration we are also transfigured through His life and testimonies within scripture. It is by Him that we are able to be changed both internally and externally; both spiritually within our hearts and through our good deeds and works.
The transfiguration of Jesus Christ was a unique display of His divine character and a glimpse of the glory, which Jesus had before He came to earth in human form. This truth is emphasized for us in a passage in the Apostle Paul's letter to Philippi.
5 In your relationships with one another, have the same mindset as Christ Jesus: 6 Who, being in very nature[a] God, did not consider equality with God something to be used to his own advantage; 7 rather, he made himself nothing by taking the very nature[b] of a servant, being made in human likeness. 8 And being found in appearance as a man, he humbled himself by becoming obedient to death— even death on a cross! 9 Therefore God exalted him to the highest place and gave him the name that is above every name, 10 that at the name of Jesus every knee should bow, in heaven and on earth and under the earth, 11 and every tongue acknowledge that Jesus Christ is Lord, to the glory of God the Father.
The transfiguration of Jesus Christ was a visible sign in the presence of reliable witnesses of the reality of the power of God and the glory, which is Christ Jesus: The Son of God came to earth in the form of a man to be the true servant of God and to gift mankind with the greatest gift ever given, eternal life.