In Romans, Paul has an extended development of the idea of slavery and liberation—fundamentally, an exodus theme. In the midst of that development, he writes in Romans 8:12 that we are debtors—not to the flesh, to live after the flesh.
That cryptic statement in context raises questions. Is this is a simple negation (“we are not debtors to the flesh”), a denial with an unspoken corresponding affirmation of where our debt genuinely rests (“we are not debtors to the flesh, but to the Spirit”), or perhaps an emphatic statement about a new situation that was previously not the case (“we are no longer debtors to the flesh”)?
Perhaps Paul doesn’t want us to answer the implicit question in just one of these ways; perhaps he wants us to acknowledge the truth of some or all of these ways of reading his statement.
It is interesting, though, to trace the idea of debtorship in connection with Paul’s theme of slavery. Under the social and de facto legal conditions of Paul’s world and Israel’s history, one could be sold into slavery for one’s debts, and was therefore bound to serve the creditor. That seems to shed some light on Paul’s argument in much of Romans 5–8, not least 6–7.
In these chapters, four powers: death, sin, flesh, and Torah all intertwine although none are interchangeable. With regard to death, sin and Torah, at least, they all have some sort of hegemony—they rule. (Intriguingly, all three are joined in the phrase of 8:2, “the Torah of sin and death”.)
For instance, death reigned from Adam to Moses, even apart from and prior to the arrival of Torah (5:14, 17; cf 6:9). Correspondingly, sin reigned in death (5:21), and it enslaved “us” (cf 6:6). And of course, Israel was under Torah, i.e. ruled by its polity.
Paul’s resolution to this is first of all that there is a new lord, a new ruler. But that fact by itself is not sufficient; what, it turns out, brings liberation into realization is not merely that Jesus rules (that’s true) but that the believer is baptized into his death (6:3).
The translations say in 6:7 that “one who has died has been set free from sin.” Aside from the fact that it’s not clear how the rather non-literal dying with the Messiah sets us free from sin, the translations are actually fudging a bit. What Paul actually says is, “The one who has died has been justified from sin.”
A couple things to note.
First, Paul doesn’t say “sins,” plural, but rather sin, singular, as if it is very nearly a personified power.
Second, again, the word is indeed justified, which is a forensic (lawcourt) term. But how is it functioning here?
I think we have an analogy in the opening of chapter 7. In his lead-in to discussing Torah, speaking to Jews (and presumably, former proselytes, those who “know Torah”), Paul says that it is only binding on a person so long as he lives, and goes on to compare the situation to a husband-wife relationship: the marriage only lasts while both partners live (7:1–2). Unexpectedly, however, Paul does not say, “Well, Torah has died, and therefore you’re no longer under Torah.” He does indeed say that believers are not under Torah, whether Jewish or not (see 7:14). But the reason is because not Torah, but you, have died to Torah by means of the (sacrificed) body of the Messiah, so that you may belong to God (7:4).
The point is that marriage is a legal condition, and in terms of biblical norms, the wife who marries someone other than her husband while both are alive is an adulteress (7:3). The husband has a legal claim upon her.
Taking this back to 6:7 and keeping in mind the background of debt slavery, I think what Paul is saying is that Sin has lost it ruling authority despite the Adamic race’s deep indebtedness to it. The judicial status has changed, not simply because Jesus is Lord, full stop, but because the believer has died with Jesus and therefore been legally released from all the powers that had previously enslaved him, whether Sin, death or Torah. This does justice (!) to Paul’s use of the term justified.
Of course, this reading does raise the question: “In what sense could Sin have a legal or judicial authority?” As puzzling as that may be (and it’s certainly worth pondering), it can be hardly a mere coincidence that not only does Paul clearly imply that Israel been under Torah; he just as clearly states that “all,” Jew and Gentile, are under Sin (3:9). The exodus story that runs through Romans is an account of liberation from the powers of death, Sin, and yes, Torah.
Going back to 8:12 again in the light of all this, I rather wonder whether the statement is ironic. It is death, Sin and Torah—powers—that rule. The flesh is man in his weakness, vulnerability and impotence, and therefore suggesting the idea of debt to the flesh is perhaps verging on sarcasm. But if we are not debtors to the flesh, and we have been liberated (justified!) from sin, death, and Torah, that leaves only one option. Abandoning the realm of the flesh that we suffered through prior to dying with the Messiah, we now live according to the Spirit who raised him (8:13).