The following is from Brendan Byrne’s commentary on Romans, pp162-164
The beginning of chapter 5 marks a major transition in Romans. Up till this point, Paul’s exposition of the gospel has focused upon faith. If Gentiles are to be included as equal citizens within the community of the saved, then faith, not the “works” of the Jewish law, must be the vehicle of the righteousness leading to salvation. Paul has locked home this principle of righteousness by faith by expounding scripture’s witness to it in the figure of Abraham, paradigm believer and recipient of the promise on the basis of faith. Now the focus shifts from faith to hope. Abandoning the fictive dialogue with a Jewish dialogue partner yet to be won to faith in Jesus Christ, Paul speaks “within” the community of believers, those whose faith has brought them right standing with God. He expounds and celebrates the hope of salvation that God’s gift of righteousness has brought into their lives, the righteousness that makes the gospel “the power of God leading to salvation for every believer-Jew first, but also the Greek” (1:16).
Towards the end of his exposition of Scripture in chapter 4 Paul had prepared the way for this transition to hope by stressing the persevering aspect of Abraham’s act of faith (4:18-21). Hope that God would make good the promise (of a son and a long line of descendants) formed an integral part of Abraham’s faith. It meant believing that the God who “gives life to the dead and calls into being the things that do not exist” (v 17) would overcome the “deadness” with regard to childbearing constituted by his own advanced age and the barrenness of his wife Sarah. In this respect Abraham’s faith is paradigmatic for Christian faith in that believers also have to hope for salvation in the face of the suffering and death characteristic of the present age. The affirmation of hope that forms the main theme of the new section of the letter that now begins (5:1-8:39) confronts what has aptly been called the “overlap” situation of present Christian life. As far as relations with God are concerned, for those justified through faith, the new age has dawned. In their bodily life, however, they remain anchored in the old age, afflicted with weakness, suffering and death. Righteousness has set them on the way but full salvation is grasped only in hope (8:23-25). The challenge is to hear the gospel in such a way that hope stays alive.
Romans 5-8 is bound together by the notable similarity in content between its two “extremities”: 5:1-21 (most specifically 5:1-11) and 8:14-39 (more specifically 8:31-39). Like bookends holding upright volumes on a shelf, these form an “inclusion” binding together the material in between. Both sections have “hope” as explicit theme, a hope that rests upon the peace with God brought about by justification (5:9; 8:31-34), attested by the Spirit (5:5; 8:14-15, 23-27). It is a hope, moreover, which confronts and endures the presence of suffering (5:3-4; 8:17-18, 35-39). Above all, the same a fortiori logic drives the argument of the two passages: hope rests upon the love of God which, having already found expression in the gift of the Son for us when we were sinners, will all the more (“much more”) certainly-now that we are God’s friends-see us through to the end (5:6, 8,9,10; 8:32).
If the hope of salvation rests upon the new righteousness brought about through faith, the challenge for believers is to preserve or live out that righteousness through to the end (the great Judgment). This explains why, just when one might consider the argument for righteousness through faith to have been won (4:25; cf. 5:1), Paul continues in this new section to skirmish with the law. To state the matter a little more accurately: as a key part of his argument for hope, he plays off the superiority of the power of the Spirit as a source of the necessary righteousness against the impotence (“weakness”) of the law in this respect. The hope of salvation is there because-not despite-the fact that “the Spirit of life in Christ Jesus has set you free from the law of sin and death” (8:2). This concern to establish the superiority of the Spirit explains the long “ethical” section that enters in between 6:1 and 8:13, before the argument for hope in the face of suffering resumes for the remainder of chapter 8.