Of the three accounts relating Christ’s transfiguration only Luke informs us of the topic discussed between Jesus, Moses and Elijah: “And behold, two men were talking with him, Moses and 
Elijah, who appeared in glory and spoke of his departure, which he was about to accomplish at Jerusalem.” (Luke 9:30). They spoke of Christ’s “departure”.
The Greek word for “departure” is literally the word “exodus”. Moses, Elijah and Jesus were speaking of Jesus’ exodus. Was this tri-person transfiguration talk a discussion of the exodus of Moses relative to the exodus of Jesus? This is likely the case, but first consider a related New Testament text that uses this Greek word exodus. The Apostle Peter wrote in 2 Peter 1:15: “And I will also be diligent that at any time after my departure (exodus) you may be able to call these things to mind.” Peter’s “exodus” is his death, as he had explained in the previous verse, “…knowing that the laying aside of my earthly dwelling is imminent.” Saint Peter’s “exodus” refers to his death, which in Christ is an exodus beyond the grave.
Does it make sense that Moses, Elijah and Jesus would be discussing the death of Jesus? Indeed it does! The death of Jesus is at the heart of Christian theology. From the fall, every human is born a citizen of Satan’s domain, born spiritually dead, born to an exodus of physical and eternal death (Eph. 2:1ff). The Savior came so that through His death He would render powerless him who had the power of death, the devil (Heb. 2:14). The Savior’s exodus reroutes our horrifying, dark exodus.
Immediately before every Biblical account of the Transfiguration, Jesus gives His initial clear prediction of His impending death and resurrection (Matt. 16:21; Mark 8:31; Luke 9:22). Jesus predicts He must be killed, and this is why He would steadfastly head to Jerusalem. Moses and Elijah “spoke of his departure (his death!), which he was about to accomplish at Jerusalem.” In the Holy City of Jerusalem the Savior would be whipped, beaten, abused and sentenced to death. Then like the Old Testament scape goat on the Day of Atonement, He would be forced out of Jerusalem, ultimately stumbling His exodus to the cross
As the Israelite’s exodus was a path into the woeful wilderness of snake-infested Sinai, so at the cross Christ’s exodus was His purposed path into Satan’s woeful wilderness of sin and death. As the Israelite’s exodus culminated in their joyous entry into the Promised Land, so Christ’s exodus culminated in the super-joyous entry into the Promised Land of resurrection to heavenly immortality.
Now, in our Baptism, we have been united with the exodus of Christ. In our Baptism we have been buried with Christ, and we have been raised to walk in newness of life (Rom. 6:3ff). In our Baptism we have a new life already. Through the Jordan of Holy Baptism we have already set our foot in the Promised Land, for even now our citizenship is in heaven from which we eagerly await the Savior who will change our vile bodies that they may be fashioned like His glorious resurrection body (Phil. 3:20,21).
Christ’s Transfiguration is an appropriate segue into Lent. During Lent we are yearly focusing on Christ’s exodus—His exodus to the cross and His exodus from the grave—realizing our exodus is accomplished in and through Him.