[Jesus] revealed His glory to the disciples to strengthen them for the scandal of the cross. His glory shone from a body like our own, to show that the Church, which is the body of Christ, would one day share His glory.The mystery of the Transfiguration is one of the Luminous Mysteries of the rosary, introduced by Pope John Paul II. Of the mystery the pope wrote in his Apostolic Letter, The Rosary of the Virgin Mary,
Each of [the luminous] mysteries is a revelation of the Kingdom now present in the very person of Jesus. ...The mystery of light par excellence is the Transfiguration, traditionally believed to have taken place on Mount Tabor. The glory of the Godhead shines forth from the face of Christ as the Father commands the astonished Apostles to “listen to him” (cf. Lk 9:35 and parallels) and to prepare to experience with him the agony of the Passion, so as to come with him to the joy of the Resurrection and a life transfigured by the Holy Spirit.