The mountain. What does this mountain signify? If we read the Gospel, we find various meanings. The mountain is, above all, the place where Jesus prayed, the place where he was alone with the Father. If we do not ascend this mountain of prayer, if we do not enter into the dialogue of Jesus with the Father, we cannot find him. The mountain is also the site of the Beatitudes, the new Sinai of the new law. The mountain is his word. To go to the mountain of Jesus means, then, to wander on the majestic mountain of his words. The mountain of the Transfiguration combines both these aspects: the Transfiguration takes place while Jesus is praying; but it is also the revelation of the true content of the books of Moses and of the Prophets. The voice of the Father is heard at this moment: “This is my beloved Son, with whom I am well pleased; listen to him.” (Matthew 17:5).
Joseph Ratzinger, Co-Workers of the Truth: Meditations for Every Day of the Year, ed. Irene Grassl, (Ignatius Press, 1992), page 316.
My notes: Bold emphasis added by me. The picture of the Mount of the Transfiguration is from the Logos Bible Software (Faithlife Corp.)