Two Testaments united at the Transfiguration
From Ephrem the Syrian, On the Transfiguration of Our Lord:
[Moses and Elijah] gave thanks to Him that their own words had been fulfilled, and with them the words of all the prophets. They adored Him for the salvation He had wrought in the world for mankind, and because He had truly fulfilled the mystery which they had themselves foretold. The Prophets therefore were filled with joy, and the Apostles likewise, in their ascent of the mountain. The Prophets rejoiced because they had seen His Humanity, which they had not known. And the Apostles rejoiced because they had seen the glory of the Divinity, which they had not known.
And when they heard the Voice of the Father, giving testimony of the Son, they learned through this that which had been obscure to them until now: that the Humanity had been assumed by Him. And together with His Father’s Voice the glory of His own Body gave testimony to Him, shining resplendent because of that within Him which partakes of the Divinity, unchangeably and without confusion. And this was confirmed by three witnesses: by the Voice of the Father, and by the presence of Moses and Elijah, who stood by Him as servants.
And they looked, the one upon the other, the Prophets upon the Apostles, the Apostles upon the Prophets. They looked upon each other, the Princes of the Old and the Princes of the New Testament. Moses the holy man looks upon Simon the sanctified. The servant of the Father looks upon the vicar of the Son… The virgin of the Old Testament looks upon the virgin of the New: Elijah looks upon John. He who had ascended into heaven in a fiery chariot looks upon him who had rested his head upon a Burning Breast. His mountain became a figure of the Church; and Jesus has united in Himself the two Testaments, which the Church receives, revealing to us that He is the Giver of both. The one received His divine secrets; the other has proclaimed the visible glory of His works.
Quoted in Oremus: A Lutheran Breviary by David A. Kind (pp.324-325)