Covenant Mediation in Romans
We open Romans 5 conscious of entering Paul's epistle in progress, with some key notions already carefully laid down by the apostle. All the world, both Jew and Greek, is under indictment to God's law, condemnation, and wrath (3:9, 19-20), so that only through the one mediator between God and man (1 Tim 2:5) through whose propitiatory death (3:25) and fulfilling of the law's demands can God's forgiveness and justification extend as a free gift to the profane and ungodly who put their trust in the Savior (3:26; 4:5-12; cf. 2 Cor 5:21; Eph 2:8-9; Titus 2"14).
Having Been Justified
Romans 5 then opens with the stunning words: "Therefore, since we have been justified by faith, we have peace with God through our Lord Jesus Christ. Through him we have also obtained access by faith into this grace in which we stand, and we rejoice in hope of the glory of God" (5:1-2 ESV). Paul says that we have now been justified and in consequence have peace, access, and standing in God's grace, which gives us sure hope for the future. This means that God has already rendered his verdict of the last day in our favor through Jesus Christ. Justification is accomplished. To all appearances, this seems to be communicated rather neatly by the lead aorist adverbial (or circumstantial) participle in 5:1: δικαιωθέντες, rendered "since we have been justified."
[Covenant, Justification, and Pastoral Ministry, The New Perspective, Mediation, and Justification, pp 148-149]