17 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!”
The Feast of the Transfiguration is a celebration of the Transfiguration of Jesus Christ.
The Transfiguration is a pivotal moment supporting the identify of Jesus as the Son of God. It also clearly marks Jesus as the messenger and voice of God when God commands them to Listen to him. He becomes the voice par excellence with Moses and Elijah representing the Law and the Prophets. The Transfiguration also clearly marks that God is the God of the living not of the Dead as both Elijah and Moses are clearly standing before the Apostles on the mountaintop.
The Roman Catholic church celebrated the Transfiguration as a feast day in various parts of the world and on different days up until around 1456. It was in 1456 that the Siege of Belgrade took place , specifically between July 4th and July 22nd. The ottoman Sultan Mehmed the Conqueror pulled together all of his military might and resources to conquer and subjugate the Kingdom of Hungary. His main object was the city of Belgrade. When news reached Pope Callixtus he ordered the bells of every church to be rung at noon of each day as a call to pray for the defenders of the city. Following a massive incursion into the city on the night of July 21st, peasant crusaders began to harrass the Ottoman line. Soon more soldiers joined them and what began as an isolated incident that morning soon turned into a full battle. John of Capistrano lead the defenders towards the Ottoman lines shouting:
"The Lord who made the beginning will take care of the finish!"
The Ottoman army was soon completely overrun. News reached Pope Callixtus III on August 6th of the victory. It was on that day that he elevated the Transfiguration to a feast day that should be celebrated throughout the entire Roman rite. Saint Pope John Paul II selected the Transfiguration as one of the five Luminous Mysteries of the Holy Rosary in 2002.
In the Byzantine Catholic and Eastern Orthodox churches, the Transfiguration falls during the Dormition Fast but allowances are relaxed with the approval of fish, wine and oil to be consumed on it. It is ranked as one of the Twelve Great Feasts and is celebrated with an All-Night Vigil the night before hand. Grapes are also brought to the church for blessing on the day of the Transfiguration as the Blessing of the Fruits.