
The story of Jesus’ transfiguration dovetails with a persistent theme in all the Gospels: Jesus’ prayer life.
The Gospels let us know that Jesus often sought out times and places for private prayer. In this, Jesus stands out from the other Biblical characters. Yes, other Biblical characters are portrayed as people of prayer — Moses, Elijah, and others — but no one more than Jesus. This runs contrary to a naive theology: as the Son of God, it seems as if Jesus would be the least in need of prayer and solitude, and the other Bible characters, being mere mortals, the most. And, maybe they were. But, Jesus was the one who sought out the place of prayer the most.
Here is the fountainhead of all subsequent teaching on the life of prayer in the various Christian traditions — the prayer life of Jesus.
Luke 9:28-31
Ἐγένετο δὲ μετὰ τοὺς λόγους τούτους ὡσεὶ ἡμέραι ὀκτὼ [καὶ] παραλαβὼν Πέτρον καὶ Ἰωάννην καὶ Ἰάκωβον ἀνέβη εἰς τὸ ὄρος προσεύξασθαι. καὶ ἐγένετο ἐν τῷ προσεύχεσθαι αὐτὸν τὸ εἶδος τοῦ προσώπου αὐτοῦ ἕτερον καὶ ὁ ἱματισμὸς αὐτοῦ λευκὸς ἐξαστράπτων. καὶ ἰδοὺ ἄνδρες δύο συνελάλουν αὐτῷ, οἵτινες ἦσαν Μωϋσῆς καὶ Ἠλίας, οἳ ὀφθέντες ἐν δόξῃ ἔλεγον τὴν ἔξοδον αὐτοῦ, ἣν ἤμελλεν πληροῦν ἐν Ἰερουσαλήμ.
“Now about eight days after these sayings Jesus took with him Peter and John and James, and went up on the mountain to pray. And while he was praying, the appearance of his face changed, and his clothes became dazzling white. Suddenly they saw two men, Moses and Elijah, talking to him. They appeared in glory and were speaking of his departure, which he was about to accomplish at Jerusalem.” (NRSV.)

It was while he was praying that “the appearance of his face changed” (τὸ εἶδος τοῦ προσώπου αὐτοῦ ἕτερον). In Exodus 34:29-35, we are told the story of Moses coming down from the Mount with the two tablets of the covenant in his hand and it says: “Moses did not know that the skin of his face shone because he had been talking with God.” (Exodus 34:29 NRSV.) This is a similar case.
I can’t state it better than H. D. M. Spence did, as he waxed eloquent in the old Pulpit Commentary:
“The marvellous change evidently passed over Jesus while he was in prayer, probably because of his intense prayer. Real, close communion with God ever imparts to the countenance of the one who has thus entered into communion with the High and Holy One, a new and strange beauty. Very many have noticed at times this peculiar and lovely change pass over the faces of God’s true saints as they prayed — faces perhaps old and withered, grey with years and wrinkled with care. A yet higher degree of transfiguration through communion with God is recorded in the case of Moses, whose face, after he had been with his God-Friend on the mount, shone with so bright a glory that mortal eye could not bear to gaze on it until the radiance began to fade away. A similar change is recorded to have taken place in the case of Stephen when he pleaded his Divine Master’s cause in the Sanhedrin hall at Jerusalem with such rapt eloquence that to the by-standers his face then, we read, “was as the face of an angel.” Stephen told his audience later on, in the course of that earnest and impassioned pleading, that to him the very heavens were opened, and that his eyes were positively gazing on the beatific vision. Yet a step higher still was this transfiguration of our Lord. St. Luke tells us simply that, ‘as he prayed, the fashion of his countenance was altered.’”

Jesus appears transfigured before them. Christ appears now in his true glory. Christ appears now in his end-of-time glory. This story is quite different than the resurrection stories — for there Jesus’ ordinariness is emphasized: he is mistaken for the gardener, he meets with the two disciples traveling to Emmaus as a conversation partner — only to be recognized for who he is in the breaking of the bread. And so forth. The resurrection Jesus is not an overwhelming presence. But, the transfiguration Jesus is: his clothes are dazzling white.
Jesus is here identified with the Shekinah glory of God. This kind of thing brought later generations of Christians to speak of Christ as: “God from God, Light from Light, true God from true God….” (The Nicene Creed.)
And, with Jesus — talking to him actually — are Moses and Elijah. They represent the Law and the Prophets. Moses and Elijah are talking to Jesus about his “departure” (ἔξοδον = exodus). They are talking to him about the events of the Cross, and resurrection, and ascension (“They… were speaking of his departure, which he was about to accomplish at Jerusalem.“) Jesus’ mission is spoken of here in terms of his giving of himself to redeem humankind.
The implicit claim here is that everything in the religious traditions of Israel are now culminating in Jesus’ death and resurrection. For us, this points to a progressive unity of the Old and New Testaments. As Jesus says in the Gospel of Matthew he comes not to abolish the law and the prophets but to fulfill them (Matthew 5:17). Faith in Christ challenges us to see the Bible record as a progressive but continuous story, culminating with the account of Jesus Christ.
Luke 9:32-34
ὁ δὲ Πέτρος καὶ οἱ σὺν αὐτῷ ἦσαν βεβαρημένοι ὕπνῳ· διαγρηγορήσαντες δὲ εἶδον τὴν δόξαν αὐτοῦ καὶ τοὺς δύο ἄνδρας τοὺς συνεστῶτας αὐτῷ. καὶ ἐγένετο ἐν τῷ διαχωρίζεσθαι αὐτοὺς ἀπ’ αὐτοῦ εἶπεν ὁ Πέτρος πρὸς τὸν Ἰησοῦν· ἐπιστάτα, καλόν ἐστιν ἡμᾶς ὧδε εἶναι, καὶ ποιήσωμεν σκηνὰς τρεῖς, μίαν σοὶ καὶ μίαν Μωϋσεῖ καὶ μίαν Ἠλίᾳ, μὴ εἰδὼς ὃ λέγει. ταῦτα δὲ αὐτοῦ λέγοντος ἐγένετο νεφέλη καὶ ἐπεσκίαζεν αὐτούς· ἐφοβήθησαν δὲ ἐν τῷ εἰσελθεῖν αὐτοὺς εἰς τὴν νεφέλην.
“Now Peter and his companions were weighed down with sleep; but since they had stayed awake, they saw his glory and the two men who stood with him. Just as they were leaving him, Peter said to Jesus, “Master, it is good for us to be here; let us make three dwellings, one for you, one for Moses, and one for Elijah” — not knowing what he said. While he was saying this, a cloud came and overshadowed them; and they were terrified as they entered the cloud.” (NRSV.)

The text implies: they almost slept through it! They were tired, but they saw it all since they had (as it happened) remained awake.
An old and unanswerable question here is: how did Peter know these were Moses and Elijah? I’ll leave you to speculate on that one….
But, it is clear that Peter is overwhelmed by this experience. Luke lets us know that he blurts out something stupid: “Master, it is good for us to be here; let us make three dwellings….” Then the cloud overshadowed them. Remember: clouds are often associated with the visible glory of God throughout the Bible. So, this is the Shekinah (שְׁכִינָה) glory of God, and they are terrified (ἐφοβήθησαν) as they enter it. While this is a form of the common verb for “fear” (φοβέω) — the verb is sometimes used to mean “reverent fear” (Mark 6:20; Luke 1:50; Acts 10:2; Ephesians 5:33; Revelation 11:18).
This, of course, is the quintessential Mountain Top Experience — a term preachers love to use. Notice: it was not sought. They were tired, but it so happened they were awake enough to experience this. And: it is not an end in itself. It is designed to impress them with the revelation of God in Christ — and their need to heed it.
Luke 9:35, 36
καὶ φωνὴ ἐγένετο ἐκ τῆς νεφέλης λέγουσα· οὗτός ἐστιν ὁ υἱός μου ὁ ἐκλελεγμένος, αὐτοῦ ἀκούετε. καὶ ἐν τῷ γενέσθαι τὴν φωνὴν εὑρέθη Ἰησοῦς μόνος. καὶ αὐτοὶ ἐσίγησαν καὶ οὐδενὶ ἀπήγγειλαν ἐν ἐκείναις ταῖς ἡμέραις οὐδὲν ὧν ἑώρακαν.
“Then from the cloud came a voice that said, “This is my Son, my Chosen; listen to him!” When the voice had spoken, Jesus was found alone. And they kept silent and in those days told no one any of the things they had seen.” (NRSV.)
Christ’s voice is the voice they must heed above all. As Christians we come to understand the preparatory messages of the Law and the Prophets in the light of what God has done and said through Christ. Christ is the key. We interpret all that has come before in the light of Christ.
The whole point of this overwhelming encounter is to cement in their minds the need to heed Jesus Christ. “This is my Son, my Chosen; listen to him!” True discipleship is more than a mountaintop experience — it is a day to day following after Christ — giving heed to his example and teaching.
John Nolland remarks in the Word Biblical Commentary:
It is not possible—and it is not right — to freeze this moment of glory. The aftermath of the voice speaks as eloquently as had the voice itself. The moment of glory has vanished. Jesus is alone. The mountaintop experience has passed and what remains is the way of the cross as the way to permanence of glory. They have seen the glory that by right belongs to Jesus, but it belongs to him the other side of death and resurrection.
The Revised Common Lectionary gives preachers the option to include Luke 9:37-43. This is the story of Jesus delivering a demonized boy — after the disciples could not help. The contrast is sharp, and this has led to the common rhetoric about “Mountain Top Experiences” versus service “in the valley.”
Prayer and service go hand in hand.

A FREE GIFT TO PREACHERS: Here is a PPTX file for a sermon based on this passage . You can use this, edit this, change this however you wish — it is free for you to use (or not). Click this link: With Christ on the Mountaintop.