But is it more than this? I am continually intrigued by Terrence Donaldson's excellent book: Jesus on the Mountain: A Study in Matthean Theology. Donaldson argues that
It is clear, against such a Christian misreading, that the contrast of "old and new" concerns the Israelite community of covenant in both its parts. The "old" covenant belongs to that Israelite community which through its sustained disobedience forfeited covenant with God, even as it lost the city of Jerusalem. The "new" covenant now wrought by God also concerns the Israelite community. This is the community formed anew by God among exiles who are now transformed into a community of glad obedience. Thus we are right to posit a deept discontinuity between old and new, but that deep discontinuity is not between Jews and Christians, but between recalcitrant Jews prior to 587 and transformed Jews after 587 who embrace the covenant newly offered by God.
[Brueggemann, A Commentary on Jeremiah: Exile and Homecoming, pg. 292]
Now the reason this intrigues me, is because I'm currently looking at the six antitheses of Matt 5:21-48. The solutions on offer at the moment suggest either that Jesus is intensifying the demands of the Torah, or that he is revising the demands of the Torah. Given the backdrop just noted, this changes everything. Jesus could be noting that the Torah applied to the people of old, the people under the leadership and direction of Moses and the teachings he gave. But given that this is a new messianic age, Jesus is giving a new set of teachings that draw from and emerge from the teachings of Torah, but go further and redirect some of it’s emphases and teachings. One could then go further and suggest that given the New Exodus theme (Wright, JVG et. al.), that Jesus envisioned his teachings replacing the demands of the old covenant, because they had been delivered from their former bondage of exile, and this was now the beginning of God's reign through the teachings of Jesus, and the Spirit, no matter where they found themselves (Matt 28:16-20). Of course this requires much annotation and justification from the sources, but I'm a BIG picture thinker, and so I'm just thinking out loud here. Thoughts?
one of the central features of Zion eschatology in the OT and throughout the Second-Temple period was the expectation of a great gathering of Israel to the holy mountain of Yahweh where they would be constituded afresh as the people of God. The gathering of the scattered flock to the holy mountain was to be the first act in the eschatological drama... In addition, one can also point to the fact that in Jewish expectation one aspect of the consummation on Mount Zion was to be a new giving of the Torah... in contemporary eschatological thought it was expected that the Messiah would bring about renewed obedience to the Torah, that he would interpret it more clearly and that he would even bring a new Torah.
[Terrence Donaldson, Jesus on the Mountain, pg. 116. See further Davies, The Setting of the Sermon on the Mount, pg. 155-156]