The Feast of the Transfiguration has been celebrated in the Eastern Church since at least the 7th century. It is believed to have its origins in the dedication of three basilicas on Mount Tabor. By the 10th century, it was celebrated throughout the Christian world, although not always on the same date. In 1456, Pope Calixtus III made the Transfiguration a universal feast to be celebrated on August 6th in commemoration of the raising of the Siege of Belgrade which repelled an Ottoman invasion.
Many scholars believe that the Transfiguration occurred during the Jewish festival of Sukkot, or the Feast of Booths. This festival commemorates the forty years the Israelites spent wandering in the wilderness and is also one of the Jewish harvest festivals. It is primarily celebrated by the building of a sukkah, or tent, in which one lives during the feast. This is one explanation for Peter’s suggestion to build tents during the Transfiguration.
Traditionally, the Feast of the Transfiguration is one of several harvest festivals celebrated in August. August 1st – the Feast of St. Peter in Chains – was also called Lammas Day and was a celebration of the first harvest of wheat during which loaves of bread would be brought to Mass to be blessed. August 15th – the Assumption – is associated with the blessing of fruits, flowers and herbs. The Transfiguration has traditionally been associated with the blessing of grapes, raisins and wine – especially in the Eastern Churches. Because Christ’s robes were transformed into a dazzling white, it is also a custom in some places to eat white foods on the Feast of the Transfiguration.