In the old theonomy discussions, Mt. 5:17 always played a prominent role. In what sense does Jesus “fulfill” the law and the prophets? But the word “fulfill” is something of a key term in Matthew’s gospel. The Greek word PLAYRAO is used 16 times in Matthew’s gospel, and in 13 of those occurrences, Matthew uses the word to describe how Jesus’ own actions or words “fulfill” what was spoken in the Law and Prophets and Writings of the Hebrew Scriptures: E.g. “So all this was done that it might be fulfilled which was spoken by the Lord through the prophet…” (Mt. 1:22, cf. 2:15, 2:17, 2:23, 5:17, 26:54, etc.).
Given the fact that Jesus is explicitly and implicitly reenacting the story of Israel, it does not seem likely that Matthew used this word 13 times accidentally. 12 is the number of the tribes of Israel, and 13 suggests that Jesus is the fulfillment of the old Israel plus one. He is Israel and yet something far greater.
But if one wanted to understand what Jesus meant by not coming to destroy the law and the prophets but rather has come to “fulfill” the law and the prophets, it seems like the first step would be to do a thorough exegetical study of all those other uses. When Matthew says Joseph and Mary’s flight to Egypt is a “fulfillment” of Hosea’s prophecy, “Out of Egypt, I have called my son…,” we ought to look at that “fulfillment” if we want to understand how Jesus came to “fulfill” the law and the prophets and not destroy them.