What did Paul mean when he had his amanuensis pen this verse? Yes, Paul did not actually pen his own epistles and if you don't know, it would be good to look up amanuensis. Why do I always digress? It must be the teacher in me LOL. Meanwhile, back to the topic at hand, seriously, what does serve in the newness of the Spirit mean? And further, what does the oldness of the letter mean? Actually today, especially in constitutional law, we frequently hear the term "spirit of the law." In this case it means what the original authors of the law had in mind when they wrote it. However, I do not think that is what Paul referred to in Romans 7:6. He was contrasting serving in the *spirit* and serving in the *letter* and the most important take-away is that they are contrasting or opposite concepts.
Yet, when one looks historically, at orthodox doctrine, it becomes crystal clear that it has a read and do focus that is akin to the Pharisees of the first century. There is no possible way that serving in the newness of the Spirit will coincide with this read and do focus. The reason is that the Pharisees focus of scripture coincides directly with the oldness of the letter. It is a polar opposite to the newness of the spirit. So what exactly is the newness of the spirit? Well, since it was contrasted with the oldness of the letter, then it must be understood to be related to scripture interpretation. I think this is precisely where the scripture focus of Jesus and his followers comes into play. As I have established over and over, in this blog, with a preponderance of evidence, Jesus, and his first century followers focus was extremely targeted. It was solely redemptive.
Jesus was the end of the law. A proper translation would be that Jesus was the goal of the law. So then, serving in the newness of the spirit, is to serve with the indwelling Spirit of Christ. The new covenant, the only covenant that includes uncircumcised Gentiles in the people of God, does not make scripture a legal-constitutional document. It only sees scripture as the story of redemption, or the redemptive narrative. Under the old covenant, Israel served in the oldness of the letter. They actually broke the covenant according to Jeremiah 31, and further to the point, they actually broke it shortly after accepting it, but still it was a legal constitutional covenant. Paul's point was that since they only had the old covenant, prior to the resurrection, they could only serve in the oldness of the letter. However, now because of the death, burial, and resurrection of Jesus Christ, which installed the new covenant, it was possible to have the indwelling Spirit of Christ, thus allowing one to serve in the newness of the Spirit.
So now, we need to look at what serving in the newness of the spirit actually looks like, and how is it accomplished practically? First, let me explain what I believe the majority opinion is on this within orthodox/evangelical doctrine. In the evangelical view, serving in the newness of the spirit involves acknowledgement that once a person is a christian, they are empowered by the holy spirit to live a lawful life; I did not say a perfect life, I said a lawful life, and by that I mean lawful form the Law of God standpoint. I do not believe that this is correct. I believe that serving in the newness of the spirit is directly related to believing the gospel message. The message that God was in Christ, reconciling the world to himself not counting their trespasses and he further made him who knew no sin to be made sin for us that we might be made the righteousness of God in Him. Believing this no matter what produces the fruit of the Spirit. It produces love for God ultimately, and that comes through peace and joy. Love, joy and peace ultimately lead to all the other spiritual fruit. However, that will only happen as one rests in the truth of the above gospel message. If you have a group/the body all rehearsing and believing the gospel, eventually, the final fruit mentioned, self-control/temperance will be there in ever increasing portions.
Romans 5:1 says it all: "Therefore, being justified by faith we have peace with God." Peace with God from hearing and believing the gospel message is the way one serves in the newness of the Spirit and not in the oldness of the letter. This is why it is necessary for seasoned saints to hear the gospel over and over and over and over again! It is likewise why Paul told the Corinthians that he determined to know nothing among them except Jesus Christ crucified... the gospel.