Intending to strengthen the human soul with the hope of eternal reward, Jesus took Peter, James, and his brother John, and led them up a high mountain. There, He revealed to them the mystery of the Trinity, foretold the humiliation of His passion, and showed them, through His transfiguration, the glory of His future resurrection. The Law and the Prophets bore witness to Him in the apparition of Moses and Elias; the Father and the Holy Spirit bore witness also, manifest as a Voice and a Cloud. And truly the soul devoted to Him, now established in the truth and raised to the summit of virtue, could make Peter's words its own and exclaim with him: "Lord , it is good for us to be here"--here, that is, in the peace and joy of seeing Your face; here, where the spirit, in a state of heavenly and ecstatic rapture, can hear secret words that man may not repeat.
Bonaventure, The Tree of Life 1.12.
[Bonaventure, The Works of Bonaventure I: Mystical Opuscula, José de Vinck, tr., Martino Publishing (Mansfield Centre, CT: 2016), p. 111.]