"Since we have been focusing of Romans 3-5 it may be helpful to see how Paul continues his argument in Romans 6-7, for here he answers explicitly an objection from an imagined interlocutor about the moral life and justification. The objection is this: "What shall we say then? Are we to continue in sin that grace may abound?" (6:1). In other words, if the grace of justification is proclaimed to sinners, should we sin more in order to magnify God's grace? Does Paul's doctrine of justification make holy living irrelevant or perhaps even undesirable? Paul explains his short answer - "By no means!" - from 6:2 through 7:6. He argues that justified believers united to Christ are no longer under the law but under grace, and that having died to the law they are no longer under the dominion of sin but bear good fruit for God and walk by his Spirit. The precise point is striking. Paul does not say that a sanctified moral life is still possible despite his doctrine of justification, which wold have answered the objection narrowly taken. What he says is that a sanctified moral life is the necessary consequence of justification and that justification is the necessary prerequisite of the sanctified moral life. Dying to the law in justification somehow results in believers for the first time being able to do the holy works acceptable before God."
David VanDrunen, Divine Covenants and Moral Order, 437