1 Finally, my brethren, rejoice in the Lord. To write the same things again is no trouble to me, and it is a safeguard for you.
2 Beware of the dogs, beware of the evil workers, beware of the false circumcision; 3for we are the true circumcision, who worship in the Spirit of God and glory in Christ Jesus and put no confidence in the flesh, 4 although I myself might have confidence even in the flesh.
Paul is reiterating something he has taught the church in the past. It is by repetition we learn things. An easy example of this is the bible. We can’t just read it cover to cover once and remember it and apply it all, can we? This is why we must not hesitate to revisit passages, even those we think we know. Time and again I have witnessed myself and from others that the bible is truly the Living Word, as we can learn different things from the same passage over and over.
The dogs, evil workers, and “mutilators” (false circumcision practitioners) are those that try to incorporate old religious practices into salvation. Granted, in Christianity we have our “traditions” but we must not do to fulfill a tradition or because we feel we have to. First of all, none of these actions actually save us. Secondly, we GET to do these things in celebration and remembrance. Doing these things don’t make you a better Christian or more worthy of grace of forgiveness, rather it is the condition of our heart that motivates us to want to do these things that matters.
This is what Paul is talking about in verse 3. He references the true circumcision. Think about that for a second. I think it is a part that is easy to slide over. Think back to the inception of circumcision in Genesis 17:
It was a covenant between God and Abraham, pouring over into the nation of Israel. The actual act of circumcision was nothing but a reminder, just like the act of taking communion. We can drink juice and eat crackers all day, but the purpose and meaning behind it is what is important. You see, Paul here is reminding us that we have a NEW covenant, the one made by Christ shedding His blood and sacrificing His life for us. We remember it by taking communion, just as the Jews remembered the covenant by circumcision.
In doing this: remembering the new covenant, we are able to worship and glorify God. However, none of us are exempt from failing again. It is that Christ did it all for us, so we have nothing to boast about. All we can do is receive it. Paul humbles himself that even he, as knowledgeable and revered as he is, is still not worthy and a sinner saved by grace, not works.