A quote from Scott W. Hahn,
Kinship by Covenant: A Canonical Approach to the Fulfillment of God's Saving Promises (New Haven: Yale University Press, 2009), p. 249, mostly for the sake of the phrase which forms the title of this post.
Careful reading of the text of Deuteronomy reveals it to be, in a sense, a self-retiring covenant. Although life through the Deuteronomic covenant was a theoretical possibility (Deut 30:15-19), both God and Moses knew and declared that, in fact, death and exile would result (Deut 30:1). Then, there would be a new initiative on God's part: a regahering of the exiles and a supernatural "circumcision" of their hearts (30:4-6). This new initiative of God involving the cleaning of the heart is what Jeremiah identifies as the new covenant (Jer 31:31).
Commenting on Galatians, Hahn continues:
For Paul, those who commit themselves once again to follow the "book of law" are attempting to rehabilitate a covenant that has failed and was -in a sense- intended to fail and thus evoke a new initiative of mercy (the circumcision of the heart) from God, which Paul sees realized in Christ.
