11 See what large letters I use as I write to you with my own hand!
12 Those who want to impress people by means of the flesh are trying to compel you to be circumcised. The only reason they do this is to avoid being persecuted for the cross of Christ. 13 Not even those who are circumcised keep the law, yet they want you to be circumcised that they may boast about your circumcision in the flesh. 14 May I never boast except in the cross of our Lord Jesus Christ, through which the world has been crucified to me, and I to the world. 15 Neither circumcision nor uncircumcision means anything; what counts is the new creation. 16 Peace and mercy to all who follow this rule—to the Israel of God.
17 From now on, let no one cause me trouble, for I bear on my body the marks of Jesus.
18 The grace of our Lord Jesus Christ be with your spirit, brothers and sisters. Amen.
In his conclusion to the Galatians Paul takes up the pen in his own hand, not so much to underscore authenticity as to draw attention to the importance of what he now has to say. This section is probably the most power packed of any in the Pauline corpus.
One last time Paul wants to go on the offensive against the Teachers. He impugns their motives, claiming that on top of being wrong, they’re insincere. The real reason why they’re making Torah observance a big issue is out of a desire to avoid persecution (note they’re given the same charge as Peter in chapter 2) being carried out by zealous Jews towards those (like many in the early church) who were soft on Torah, especially on Jewish identity markers like circumcision. If they could convince the Gentile Galatians to become Jews then, rather than being persecuted, they would be lauded and have grounds for boasting.
In vv. 14-15 we see the strong apocalyptic themes in Paul’s thought. The time for defining the people of God by Torah is a thing of the past. Torah with its inherent division of humanity into Jew and non-Jew is a thing of the past. All distinctions have been erased by the cross. The problem of the Teachers isn’t that they’re Jewish, it’s that they’re trying to restrict the people of God ethnically. ‘Here too, the irony of Paul’s critique should not be missed: the very appraisal of circumcision by which Jews typically saw themselves as marked out from the wider world (as special to God) was itself a mark of belongingness to the world in its distance from God and deserving of God’s judgment’ (Dunn 342 - emphasis original).
Paul concludes with words of blessing and a hopefulness that the Galatians will ultimately be on his side. Sandwiched in there is his wish to not have to deal with this issue again. His cruciform lifestyle was self evident and should have been all of the testimony he needed of his genuine apostleship.