Paul's letter to the Galatians is an important text for reflecting on the continuities and discontinuities of redemptive history. On the one hand, Paul argues for a massive discontinuity between Israel and the church, insisting that the coming of Christ decisively undermines the division of Jew and Gentile (Gal. 2:11-16; 3:23-29). At the same time, Paul is at pains to show that this change is precisely in keeping with the purposes of God already expressed to Abraham (3:1-14), so that the "new thing" is inherently a very old thing, a thing older even than the law, which was added as a means for realising the Abrahamic promise (3:19). From Galatians, one might draw this rule of thumb: any "new thing" in the church that is not simultaneously the realisation of some "old thing" represents a false path.
Peter Leithart, 1&2 Kings (SCM Theological Commentary on the Bible), p.253
