Here’s Romans 3:24-25:
… and are justified by his grace as a gift, through the redemption that is in Christ Jesus, whom God put forward as a propitiation by his blood, to be received by faith. This was to show God’s righteousness, because in his divine forbearance he had passed over former sins. It was to show his righteousness at the present time, so that he might be just and the justifier of the one who has faith in Jesus (ESV).
And now, from Jonathan Gibson’s essay on definite atonement in the Pauline epistles in From Heaven He Came and Sought Her: Definite Atonement in Historical, Biblical, Theological, and Pastoral Perspective
In this passage, Paul spotlights God’s justice in presenting Christ as a propitiation. The propitiatory atonement of Christ vindicates God’s justice, retrospectively and prospectively (vv. 25-26). With respect to the past, Paul states that God’s punishment of sin at the cross justifies his passing over sins previously committed (v. 25). But whose sins? … The faith community of the old covenant is surely in view, since Paul goes on to speak of God’s justice at the present time in justifying those who have faith in Jesus — the faith community of the new covenant. Indeed, in Romans 4, to bolster his argument for justification by faith alone, Paul speaks of the forgiveness of Abraham and David on the basis of their faith, both of whose sins were definitely passed over until they were punished in Christ. If the “former sins” to have a universal reference, then one has to ask what Christ’s propitiatory death accomplished for the sins of Pharaoh and the Egyptians, for example. It makes more sense to understand the “former sins” to be those of the OT faith community, and thus, in this regard, the atonement that Christ offered already had a particular focus. It seems reasonable, then that it would also have a definite reference in the “present time.”
Previously posted quotes from this book.