The Transfiguration of the Lord: "the Ancient One took his throne"

His clothing was bright as snow, and the hair on his head as white as wool; his throne was flames of fire, with wheels of burning fire. A surging stream of fire flowed out from where he sat; Thousands upon thousands were ministering to him, and myriads upon myriads attended him. The court was convened and the books were opened.

-- Dn 7:9-10, 13-14

On the threshold of the public life: the baptism; on the threshold of the Passover: the Transfiguration. Jesus' baptism proclaimed "the mystery of the first regeneration", namely, our Baptism; the Transfiguration "is the sacrament of the second regeneration": our own Resurrection. From now on we share in the Lord's Resurrection through the Spirit who acts in the sacraments of the Body of Christ. The Transfiguration gives us a foretaste of Christ's glorious coming, when he "will change our lowly body to be like his glorious body." But it also recalls that "it is through many persecutions that we must enter the kingdom of God":

Peter did not yet understand this when he wanted to remain with Christ on the mountain. It has been reserved for you, Peter, but for after death. For now, Jesus says: "Go down to toil on earth, to serve on earth, to be scorned and crucified on earth. Life goes down to be killed; Bread goes down to suffer hunger; the Way goes down to be exhausted on his journey; the Spring goes down to suffer thirst; and you refuse to suffer?"

-- CCC 556