Circumcision wasn't a requirement for salvation. It was a sign of the covenant God had with Israel.
Originally Posted by kjijujoseph
We are taught that Abraham was saved BEFORE circumcision.
9 Is this blessedness only for the circumcised, or also for the uncircumcised? We have been saying that Abraham's faith was credited to him as righteousness. 10 Under what circumstances was it credited? Was it after he was circumcised, or before? It was not after, but before! 11 And he received the sign of circumcision, a seal of the righteousness that he had by faith while he was still uncircumcised. So then, he is the father of all who believe but have not been circumcised, in order that righteousness might be credited to them. 12 And he is also the father of the circumcised who not only are circumcised but who also walk in the footsteps of the faith that our father Abraham had before he was circumcised.
In fact, the first several chapters of Romans will develop this topic for you
Grace to you
If we doubt or do not believe that God is gracious to us and is pleased with us, or if we presumptuously expect to please Him only through and after our works, then it is all pure deception, outwardly honoring God, but inwardly setting up self as a false [savior].... (Part X. XI) Excerpts from Martin Luther, Treatise Concerning Good Works (1520).