I have a ten part series on the subject of the Transfiguration coming out over on Reformation21. The first part has just been posted.
The events of the Baptism and Transfiguration themselves are similar in some noteworthy respects. When he was baptized, the Spirit descended upon Jesus in the form of a dove, and the Father’s voice declared Jesus to be his beloved Son, in whom he was well pleased. At the Transfiguration, the Spirit descends in the form of the bright glory cloud  and the voice of the Father announces that Jesus is the Chosen Son, and that the disciples should hear him. Understood in such a manner, both the Baptism and the Transfiguration are overtly Trinitarian theophanies. In Luke’s gospel, there is also a characteristic emphasis upon prayer common to both accounts: both of the events occur while Jesus is praying (3:21-22; 9:29). Such associations between the Baptism and the Transfiguration–great disclosures of Christ’s glory and mission that initiate successive stages of his earthly ministry–are indications, far from being an anomalous event within the larger plot, the Transfiguration may be structurally integral to the progression of the gospel narratives.