“Sinner” is an identity word and is misapplied if it’s used to name the Christian’s identity—their person. Before God, identity is not a both/and (sinner and righteous); it is an either/or (sinner or righteous). The basis of this difference is not anthropological (what I do or don’t do). It is strictly and solely Christological: to be in Christ is to be righteous before God.
Paul does something unprecedented (in comparison with early Jewish literature) in that he designates all people outside Christ with the identity “sinner” (Romans 5:8, for example). But even more novel and scandalous is his corresponding claim that it is precisely “sinners” who are identified as “righteous” in Christ (Romans 3:23-24). So, to borrow an expression from a Reformation confession, while the old Adam is a “stubborn, recalcitrant donkey,” this does not define Christian identity before God....
The pastoral payoff here is that it enables us to affirm (without crossing our fingers) that in Christ—at the level of identity—the Christian is 100% righteous before God while at the same time recognizing the persistence of sin. If we don’t speak in terms of two total states (100% righteous in Christ and 100% sinful in ourselves) corresponding to the co-existence of two times (the old age and the new creation), then the undeniable reality of ongoing sin leads to the qualification of our identity in Christ: the existence of some sin must mean that one is not totally righteous. This is acid at the very foundation of the peace we have with God on the other side of justification. To say simul iustus et peccatoris [simultaneously righteous and a sinner] is therefore not to say that “sinner” is our identity; it is to say that while we remain sinful in ourselves we are, in Christ, totally righteous.
This pastoral pattern is reflected in 1 Corinthians. In themselves, the Corinthians are anything but sanctified saints: they are quarreling and creating factions around various Christian leaders; they are taking one another to court; sexual immorality is rampant; the bodily resurrection is being denied; worship is chaotic. But writing to these people in the face of this sin, Paul addresses them as “those sanctified in Christ Jesus, called to be saints” (1 Corinthians 1:2). The possibility of this kind of speech is anchored in a distinction between who the Corinthians are in themselves and who they are in Christ. This confident and creative “calling”—this naming of a person in terms of who they are in Christ—is the catalyst of change. To call a person by their “new name” is to summon them away from faith in themselves–away from the sin and death that defines the old age–and to summon them to faith in Christ, to the salvation and status that defines the new creation and the Christian as one whose identity is “hid with God in Christ.”
Taken from “Simultaneously Righteous and a Sinner?” (used by permission).