The Transfiguration is a "theophany," a revelation or manifestation of the mystery of God. If the Epiphany was the manifestation of Christ to the Gentile world, though still veiled in his humanity - he was revealed to them as a baby - the two explicit theophanies of the New Testament, the Baptism and the Transfiguration, are clearer glimpses of his divinity. Of course, even these were somewhat veiled. We will only see Christ in all his glory through the elevation of our nature in the Beatific Vision, after the resurrection from the dead, for as God said to Moses, in our fallen state, "My face you cannot see, because no one can see it and be left alive." (Exodus 33:20). However, in both episodes, Christ revealed something of his divine reality. It was like briefly drawing back the curtain of heaven. As Matthew says: "the heavens opened" (Matthew 3:16).
In the transfiguration, Peter, James and John were introduced into the very life of God. Within this Trinitarian life they found two great Old Testament figures in dialogue with Christ: "Suddenly, two men were conversing with him: they were Moses and Elijah, who, appearing in glory, spoke of his exodus, which he was to consummate in Jerusalem.". The righteous in heaven participate in God's concern for the redemption of mankind and are informed of its key aspects. In heaven we are not passive spectators, as the book of Revelation shows (e.g., Rev. 5:8; 6:10-11; 8:3-4).
The apostles enter into the Trinitarian glory, expressed by the presence of Christ the Son, the voice of the Father and the cloud that simultaneously expresses and conceals the Holy Spirit. This provokes fear in them and at the same time inspires them with joy, with the desire to prolong the experience. "Peter said to Jesus: 'Master, how good it is that we are here! We will make three tents...', I didn't know what I was saying.".
Heaven is too much, too good, for poor fallen humans. It makes us dizzy, it almost makes us drunk! Every form of prayer is, in its own small way, entering into the Trinitarian life. There we meet the Father, the Son and the Holy Spirit; we are joined by the righteous in Heaven (cf. Hebrews 12:1); and we are asked to listen to and obey Christ: "This is my Son, the Chosen One; listen to him!". Then, unfortunately, as wayfarers on earth, we have to return from the mountain of prayer to all the fuss at the base of the mountain, that is, to ordinary life (cf. Luke 9:37ff), and, ultimately, to sharing with Christ in his Passion.
