The new life in which we can walk (Romans 6:4) as new creatures, slaves to God and righteousness, in turn presupposes being set free from slavery to sin (6:18). Thanks be to God for that (6:17), because it is He, not we, who made such both possible and actual through the work of His Son. How have we been set free from sin? We have been crucified with Christ and raised with Him (6:5). His death and resurrection have defeated sin (6:9-11), and only by being united with the righteous Messiah by grace, through faith, and in His Spirit, we are now able to obey and do good works as slaves to a new and infinitely better Master. In short, our justification precedes our sanctification, and as we are united to the Son who is Lord over all facets of our salvation, we will experience all facets. As facets of our salvation, sanctification and eternal life are fruits of a life of slavery to God, of obedience and good works. Thus, the latter necessarily follow the former, although they do not function as the meritorious ground for such ends.
So being under grace rather than law does not mean we should live lawlessly (6:15). We should present our members or persons as slaves to righteousness – which implies obedience (6:16) to some standard or law – and if we do not, we are living a life which has not been set free from sin, a lawless life which ironically keeps us under “the law” and its demand for sinless perfection. Just as union with Christ pervades the life of believers, union with sin pervades the life of unbelievers. Practicing sin evidences a life which has not been freed from sin (John 8:34). A life of practiced love for the greatest and second greatest commandments is a life that fulfills the law (Romans 13:8-10) and can do so precisely because it is not attempting to be justified by it – to live under it.
Now, while Paul speaks in “human terms” (6:19) when he talks about our slavery to God, it is also clear that he also considers us free. To be a slave to one master is to be free from another. When we are slaves to sin, we are free from righteousness (Romans 6:20). Is that the sort of freedom we want? Paul speaks of our slavery as either to sin leading to death or God leading to eternal life (6:16). To which of these ends does pretending to be our own, “free” masters lead?
We should then endeavor to be free from sin just as we were free from righteousness, and our freedom is deeper. Elsewhere, both Paul and Jesus contrast slavery to sin with freedom in sonship:
John 8:34-36 Jesus answered them, “Truly, truly, I say to you, everyone who practices sin is a slave to sin. The slave does not remain in the house forever; the son remains forever. So if the Son sets you free, you will be free indeed.
Galatians 4:21-26 Tell me, you who desire to be under the law, do you not listen to the law? For it is written that Abraham had two sons, one by a slave woman and one by a free woman. But the son of the slave was born according to the flesh, while the son of the free woman was born through promise. Now this may be interpreted allegorically: these women are two covenants. One is from Mount Sinai, bearing children for slavery; she is Hagar. Now Hagar is Mount Sinai in Arabia; she corresponds to the present Jerusalem, for she is in slavery with her children. But the Jerusalem above is free, and she is our mother.
Slavery corresponds to sonship. As slaves to God, we are in turn regarded as sons of God, and our sonship gives us an inheritance (Galatians 4:30) that slavery to sin and sonship to the devil (John 8:44) does not. But our new life of “slavery” is not only freedom from sin but also the freedom of a gifted promise (Romans 6:23), because our new Master is really a new Father. Or, in divine rather than human terms,
Galatians 4:7 So you are no longer a slave, but a son, and if a son, then an heir through God.