Romans 3.31- “Do we then overthrow the Law by this faith? By no means! On the contrary, we uphold the law.” This is one of many verses in the NT that has helped me to reinterpret what was perhaps my shallow understanding of the OT. The reason Paul might pose this hypothetical question that a Jewish Christian might have is because of how clear he is being about justification by faith alone. He is highlighting that central gospel truth to the point where it sounds like the Law of Moses is being abolished.
But Paul’s response is “NO!” By putting our faith in Christ we are not abolishing or overthrowing the Law– we are actually upholding it! In other words, you should have understood that the Law back in Exodus-Deuteronomy was pointing to a Messiah who you needed to trust in to fulfill the Law for you. If you understood that you would have been understanding the Law rightly. By putting your faith in Jesus Christ, you are upholding the intent of the Law! It has never been about ethnicity, it has always been about personal faith in the Messiah.