What does it mean to serve in newness of spirit rather than the oldness of the letter?
It means believers are delivered from the Law, which was an administration of death, and now serve in the spiritual realm rather than under the Law's letter. This new life and frame of thinking comes by believing the Gospel, not by returning to legalism or fleshly Law-keeping.
Les explains that being delivered from the Law means we are no longer held by that administration of death. Instead, believers now serve in newness of spirit, which is the whole transformation of life in the spiritual realm, not the oldness of the letter. The letter refers to the Law. We are not under that Law, but are now in a whole new frame of thinking, the spiritual realm. Les asks how we get there: believe the Gospel. He ties this to Galatians 3:3, where having begun in the Spirit by Paul's Gospel through faith plus nothing, they should not try to move into a deeper spiritual life by the flesh. The flesh in the Galatian churches wants legalism and Law; it is part of the old Adamic nature to want to be under some kind of Law. Galatians 3:4-5 continues that warning about suffering so many things in vain.
But now we are delivered from the law, that being dead wherein we were held; that we should serve in newness of spirit, and not in the oldness of the letter.
More Questions
What does it mean to serve in newness of spirit in Romans 7:6?
Serving 'in newness of spirit' means serving under the control of the Holy Spirit, under the control of the Word of God, and under the control of the Creator God Himself—not in the oldness of the letter or the law.