Citations: Matthew 17:1-13 || Mark 9:2-13 || Luke 9:28-36 Setting: ~6-8 days after Peter's confession (Matthew 16:13-20). Jesus takes Peter, James, John up "a high mountain apart", traditionally identified as Mount Tabor in Galilee or Mount Hermon further north.
Narrative
Jesus is "transfigured" (μετεμορφώθη metamorphōthē) before them, his face shines like the sun; his clothes white as light. Moses + Elijah appear talking with him. Luke uniquely notes the conversation topic: "his departure (ἔξοδος exodos), which he was about to accomplish at Jerusalem" (Luke 9:31).
Peter (always Peter): "Lord, it is good for us to be here. If you want, let’s make three tents here: one for you, one for Moses, and one for Elijah." Mark adds: "for he didn't know what to say, for they were very afraid."
A bright cloud overshadows them. Voice from the cloud: "This is my beloved Son, in whom I am well pleased. Listen to him." Disciples fall on faces; Jesus touches them: "Get up, and don't be afraid." They look up; Jesus alone.
Coming down (Matthew 17:9-13): Jesus charges them not to tell the vision until "until after the Son of Man had risen from the dead" They ask why scribes say Elijah must come first. Jesus: "Elijah indeed comes first… but I tell you that Elijah has come already, and they didn't recognize him." Disciples understand he speaks of John the Baptist.
Theological significance
Confirmation of Peter's confession, Peter's "you are the Christ, the Son of the living God" (Matthew 16:16) is divinely attested a week later: "This is my beloved Son" (Matthew 17:5).
Moses + Elijah symbolism, Moses = the Law; Elijah = the Prophets. Together they represent the entire OT testimony. Their conversation with Jesus about his "exodus" frames Jesus's death + resurrection as the fulfillment of Law + Prophets. The voice's "Listen to him" then shifts authority to Jesus.
Pre-resurrection appearance of resurrection glory, Peter, James, John see what the disciples don't see again until Revelation 1. The transfiguration anticipates resurrection-state + the heavenly Christ.
Cloud-glory connection, the bright cloud is the Shekinah glory of the Tabernacle (Exodus 40:34-35), the temple (1 Kings 8:10-11), and the wilderness pillar of cloud (Exodus 13:21-22). Yahweh's manifest presence covers + endorses the Son.
Anticipation of the Olivet "coming with clouds", Matthew 24:30; Matthew 26:64 (Jesus's trial reply). Peter later cites the transfiguration as eyewitness evidence (2 Peter 1:16-18): "we were eyewitnesses of his majesty" … "We heard this voice come out of heaven when we were with him on the holy mountain."
Trinity-visible-moment, Father (voice from cloud), Son (transfigured), Spirit (overshadowing cloud, connecting to Luke 1:35 annunciation pattern + Exodus 40 Tabernacle pattern). Traditional trinitarian reading.