This no KEY. There is no mystery here. Paul is referring to Jews and Gentiles. Circumcision vs. non-circumsized. Circumcision was the outward sign of the promise given to Abraham. Circumcision by faith refers to the inward change to the heart of the believer by which the world would know who had the promise of salvation paid for by Christ. No Law here again. Paul doesn't ever talk about 10 commandment justification because it doesn't exist.
How doesn't this answer your question?
What does circumcision have to do with justification?
Nothing, just like the Law has nothing to do with justification just as Paul writes Rom 3:20; 28.
You say:
How doesn’t this answer your question?
You answer totally and completely wrong. You, like all the millions of false prophets, miss the whole point of Paul’s teachings and why he talks about the circumcision. Paul was sent to the gentiles specifically to teach them that salvation into the promised land no longer required the physical sign of the circumcision, as the old Testament taught, to be an heir or adopted son. The Jewish Pharasees hated Paul, Yeshua or anyone who preached the salvation through non physical circumcision because they wanted the promises of the land covenant all to themselves. They don’t want to share the inheritance with the dogs. The parable about Lazarus (gentile) and the rich man (Pharisee) demonstrates this same point. So many, like you, just don’t understand the Bible. You preach things that you don’t understand.
You say:
the Law has nothing to do with justification just as Paul writes Rom 3:20; 28.
Again you box yourself into a corner which is nothing new. Are you contradicting James, speaking of the big 10 ?
Jam 2:12 ….they that shall be judged by the law of liberty.
It has become very obvious that you are very confused. I guess you think that Paul speaks about circumcision just to hear himself talk or maybe you think he’s perverted or something. Why doesn’t he talk about the heart, or something else concerning the physical anatomy? You obviously are blind to the relationship of circumcision and justification as taught by Paul, which is about most of the New Testament. You need to read and understand the OLD before you try to understand the NEW.
Blessings as you search for TRUTH.