For Matthew, Jesus is the preacher who completely fulfills the priestly role of teaching the Law of Moses and the prophetic role of proclaiming the Word of God. That Jesus fulfills the role of preacher from the standpoint of both the Law and the prophets is particularly clear from the story of the transfiguration (Matt. 17:1-8). What the disciples saw on the mountain at that illuminating moment was that Jesus was the one who spoke to Moses on Mount Sinai and from whom Elijah heard the still, small, prophetic voice on the mountain.
Hughes Oliphant Old, The Reading and Preach of the Scriptures in the Worship of the Christian Church: Volume 1: The Biblical Period (Grand Rapids: Eerdmans, 1998), 137.