Moses upon the mount of transfiguration was a witness to Christ's victory over sin and death. He represented those who shall come forth from the grave at the resurrection of the just. Elijah, who had been translated to heaven without seeing death, represented those who will be living upon the earth at Christ's second coming, and who will be "changed, in a moment, in the twinkling of an eye, at the last trump;" when "this mortal must put on immortality," and "this corruptible must put on incorruption." 1 Corinthians 15:51-53. Jesus was clothed with the light of heaven, as He will appear when He shall come "the second time without sin unto salvation." For He will come "in the glory of His Father with the holy angels." Hebrews 9:28; Mark 8:38. The Saviour's promise to the disciples was now fulfilled. Upon the mount the future kingdom of glory was represented in miniature,--Christ the King, Moses a representative of the risen saints, and Elijah of the translated ones. ...
But before the crown must come the cross. Not the inauguration of Christ as king, but the decease to be accomplished at Jerusalem, is the subject of their conference with Jesus. Bearing the weakness of humanity, and burdened with its sorrow and sin, Jesus walked alone in the midst of men. As the darkness of the coming trial pressed upon Him, He was in loneliness of spirit, in a world that knew Him not. Even His loved disciples, absorbed in their own doubt and sorrow and ambitious hopes, had not comprehended the mystery of His mission. He had dwelt amid the love and fellowship of heaven; but in the world that He had created, He was in solitude. Now heaven had sent its messengers to Jesus; not angels, but men who had endured suffering and sorrow, and who could sympathize with the Saviour in the trial of His earthly life. Moses and Elijah had been colaborers with Christ. They had shared His longing for the salvation of men. Moses had pleaded for Israel: “Yet now, if Thou wilt forgive their sin—; and if not, blot me, I pray Thee, out of Thy book which Thou hast written.” Exodus 32:32. Elijah had known loneliness of spirit, as for three years and a half of famine he had borne the burden of the nation’s hatred and its woe. Alone he had stood for God upon Mount Carmel. Alone he had fled to the desert in anguish and despair. These men, chosen above every angel around the throne, had come to commune with Jesus concerning the scenes of His suffering, and to comfort Him with the assurance of the sympathy of heaven. The hope of the world, the salvation of every human being, was the burden of their interview. [/size][/color]
Moses and Elijah were sent to encourage Jesus at the end of His ministry and to help Him face the approach and endurance of the agony of the trial, cross, death, and completion of the plan of salvation and is in miniature of His 2nd Advent. It was also I believe placed in scripture that we may study the lives of Moses and Elijah; see the trials and agonies they went through and were victorious through Christ that as we come into the trials and tribulations of our lives and the trials and tribulations at the end of time, we can see we also can come through with the faith of Jesus, being raised from the dead or be part of the 144,000 that live through the tribulation. We can see Jesus in the clouds of glory at His 2nd Advent.