Paul in Galatians 6:12–15:
12 It is those who want to make a good showing in the flesh who would force you to be circumcised, and only in order that they may not be persecuted for the cross of Christ. 13 For even those who are circumcised do not themselves keep the law, but they desire to have you circumcised that they may boast in your flesh. 14 But far be it from me to boast nexcept in the cross of our Lord Jesus Christ, by which the world has been crucified to me, and I to the world. 15 For neither circumcision counts for anything, nor uncircumcision, but a new creation.
Thomas Schreiner comments on 6:15 in his Galatians commentary [(Zondervan, 2010), pages 379–380; my emphasis]:
Since the world has been crucified to Paul (and by extension to all Christians), whether one is circumcised or not is utterly irrelevant. What is remarkable is that circumcision is assigned to the old world order, to the old creation rather than the new creation. The law is part of the old age, while the cross inaugurates the new age.
The centrality of the new creation functions as an envelope with the introduction to the letter, where the death of Christ delivers from the present evil age (1:4). The new creation has dawned, in other words, through the cross of Christ.
We see the same dynamic in 2 Cor 5:14-21. There Paul also features the new creation, and again it is tied inextricably to the cross of Christ. The new creation has been inaugurated in Christ and will be consummated at the eschaton, when the groaning that characterizes the old creation will pass away (Rom 8:18-22).
Remarkably, in the midst of a great conflict over circumcision, Paul does not elevate uncircumcision either. Those who find significance in uncircumcision belong to the old world order as well. There is no particular virtue in uncircumcision, which explains why Paul was willing to circumcise Timothy (Acts 16:3). If circumcision is practiced for cultural reasons and not to achieve salvation, observing it is up to one’s individual conscience.
Verse 15 parallels both 5:6 and 1 Cor 7:19. The faith that expresses itself in love (5:6) is now a reality because the new creation has dawned. The ability to keep God’s commands is a reality in the new creation (1 Cor 7:19). Eschatology, then, plays a vital role in Galatians, for the Judaizers were attached to the old age and failed to see that the new has come. Their error, however, was not merely eschatological; there were anthropological corollaries and causes, for those who are attached to the old age cling to it because they desire to establish their own righteousness instead of receiving the righteousness from God (cf. Rom 10:3).
This is one way that eschatology reframes the personal struggle with self-righteousess and legalism (but without in any way diminishing the priority of personal obedience).
If you find it difficult to release your grip on your own self-righteous before God, you’re not alone, it is a problem we all face as sinners. The solution is found in turning away from the old age and living in light of the new age that began in the death and resurrection of the Savior. The eschatology of the New Testament, here in Galatians, will serve us well in our struggle to release our grip on self-righteousness.