For Peter—as, indeed, for the whole Church—the transfiguration of Jesus on Mount Tabor became a testimony to His majesty. What happened there? The apostles undoubtedly saw their Teacher on Tabor in a transfigured body, a body that by its nature belongs to the Kingdom, the same kind of body in which they would later see Him risen. But what was the meaning of the vision? And what had preceded it in the Yahwist and Jewish traditions?

This was, quite clearly, a revelation of the Kingdom. Such revelations had been known since ancient times. Visions of the Throne of Glory had become part of the liturgical tradition as early as Solomon's era, and they were nothing other than revelations of the Kingdom. The Kingdom had not yet “drawn near,” of course, but its glimmers would nevertheless sometimes penetrate the untransfigured world. At times it was partly revealed in other ways as well, particularly in visions of Yahweh's heavenly chariot, such as the one Ezekiel saw. That chariot bore the same Throne of Glory that others—Isaiah of Jerusalem, for example—saw in the Temple.

Now the vision of the transfigured Saviour took the place of the vision of the Throne of Glory. This too, of course, was a revelation of the Kingdom, and the apostles understood it perfectly. They failed to understand only one thing: for the Kingdom to enter the world definitively, the Messiah had to follow His path to the end, and that end would be not victory in a messianic war but death on the cross followed by resurrection. Yet the fact that Jesus appeared before the apostles in this way became convincing testimony for them that He was the Messiah. The Kingdom belongs to the Messiah, and if their Teacher now appeared before them as King—as was evident—then He truly was the Messiah, and the Kingdom truly belonged to Him. It is no accident that, precisely after the vision on Tabor, Jesus Himself began to speak especially often and at length with the apostles about His death and resurrection. They now knew almost everything; what remained was for them to grasp the essential point: exactly how the Kingdom would enter the world.

Yet the essential point proved to be the hardest, above all because it contradicted every accepted notion of the Messiah and the Kingdom at that time. The misunderstandings faded after Pentecost, but the memory of this remarkable event remained—and was preserved by the Church.

Peter is speaking here first of all about his own experience of communion with Christ. But he does not mean only the fact that he was with Jesus during His earthly ministry. The apostle draws attention above all to his experience on Mount Tabor, to the experience of the Transfiguration. And to his encounter with the risen Jesus, who foretold his death as a martyr. It is precisely these words of the Savior, spoken to Peter after His resurrection, that the apostle recalls when he says that he will soon have to “leave this dwelling,” evidently meaning his physical body and thus his earthly life.

For the apostle, as we can see, what matters most is not the experience of simply being beside Jesus, but the experience of sharing with Him in the reality of the Kingdom that He brought into the world. Both the Transfiguration and the Resurrection are experiences of the Kingdom, and it is on these that Peter focuses his attention. He bears witness first and foremost to his own experience of the Kingdom—as, indeed, do all the apostles, for Christianity is nothing other than life in the Kingdom.

But alongside his own experience, Peter also invokes another: the experience of the prophets. This is the experience reflected in the Sacred Scripture of the Jews—the prophetic books having already formed part of Judaism's Sacred Scripture in the Gospel era. It was a reference both to Sacred Scripture and to Tradition, for Tradition was founded on the prophetic books no less than on the Torah. For Peter, however, Tradition is inconceivable without what today is sometimes called its charismatic component. To interpret the texts of the prophetic books adequately, one must have the same spiritual experience as the prophets had, or at least a similar one. Otherwise, nothing will come of it.

This is the essence of genuine Tradition, with a capital T: it cannot be preserved like food sealed in a jar. For Tradition with a capital T, to preserve means to recreate and experience anew, making present here and now what the authors of the relevant texts experienced in their own time. Genuine Tradition then becomes part of the experience of the Kingdom, and therefore part of the new, now Christian, Tradition. It becomes part of the Church's experience as well, for the Church is the Kingdom on earth.

God develops His relationship with humanity as a dialogue unfolding through time. He lets the prophet Daniel see how the Son of Man receives power and glory from the heavenly Father; then the Son of God, who came in the flesh, calls Himself the Son of Man so that people can relate this to the prophecy they know. When a person responds and confesses the Son of Man as the Son of God, as Peter did, a new revelation is given to him: the Transfiguration of the Lord, foreshadowing the coming Resurrection, so that the disciples may later meet and recognise the Risen One.

And the dialogue does not end there; it never ends. The fullness of Revelation is in Christ Jesus, but the unfolding of that fullness is a dynamic process taking place in the Church, which preserves everything it has received and guides all nations towards a deeper relationship with God.