But now (meaning, as things are, not at the present time, as is shown by the aorist following) we have been (properly, we were) delivered ( κατηργήθημεν, the same verb as in Romans 7:2; see note on that verse) from the Law, having died to that wherein we were held; so that we serve in newness of the Spirit, and not in oldness of the letter.
In the word "serve" ( δουλεύειν) we observe a resumption of the idea of Romans 6:16, seq., where we were regarded under the aspect of being still bond-servants, though to a new master. There the apostle intimated that he was but speaking humanly in describing our new allegiance to righteousness as bond-service, such as we had once been under.
Here he intimates the true character of our new service by the addition of the words, ἐν καινότητι πνεύματος καὶ οὐ παλαιότητι γράμματος. These are characteristic and significant expressions. "Spirit" and "letter" are similarly contrasted (Romans 2:29; 2 Corinthians 3:6).
"Spiritum literae opponit, quia antequam ad Dei voluntatem voluntas nostra per Spiritum sanctum formats sit, non habemus in Lege nisi externam literam; quae fraenum quidem externis nostris actionibus injicit, concupiscientiae autem nostrae furorem minime cohibet.
Novitatem. vero Spiritui attribuit, quia in locum veteris hominis succedit; ut litera vetus dicitur quae interit per Spiritus regenerationem" (Calvin). Otherwise, with regard to newness and oldness, "Vetustatis et novitatis vocabulo Paulus spectat duo testamenta" (Bengel).
That the latter idea may have suggested the expressions seems not unlikely from 2 Corinthians 3:6-18 (cf. also Hebrews 8:6-13). For in both these passages the idea of the verse before us enters, and in both the old and new covenants are contrasted with regard to it.
It may be enough here to say that the contrast in its essence is between exacted conformity to an external code (which was the characteristic of the old covenant) and inspired allegiance to the Law of God written on the heart (which is the characteristic of the new).