“… so that in him we might become the righteousness of God”
Apart from a few unfortunate comments, which are by the way, Wright’s exegesis of 1 Corinthians 5:21 is penetrating. Here is a summary of the argument from pages 159-163 in Justification:
In context, Paul is talking about, defining (and defending), his apostleship. The characteristics of apostleship are as follows: “We are the aroma of Christ” (2:15). Our sufficiency, for this office and work, is from God (2:16), who has made us competent ministers of the new covenant (3:5-6), which, in the Spirit, because of Christ, gives life, and freedom, in which we [apostles and those to whom they minister in the new covenant] behold the glory of the Lord, being “changed into his likeness” (3:6-18). The Corinthians see this light in the ministry of the apostles, despite the apostle’s humble appearance (4:1-7). Jesus is manifested in their bodies (4:10). The apostles are motivated by the fear of the Lord, and the Corinthians ought to be proud of them, not because of merely extrinsic position, but because of the rootedness of this position in the heart (5:10-12).
[I would argue that this bit of the passage is indicative of a supernatural/sacramental dimension of apostleship; wherein the heart is not opposed to the office, but the office is grounded in the grace bestowed in ordination.]
Christ died for all, and has brought about a new creation, therefore, the ministry which he has entrusted to us, the ministry of reconciliation (by God, of the world, in Christ, to God), ought not to be regarded from a merely human point of view (5:14-19). Therefore, we are ambassadors of Christ, through whom God makes his appeal to the world, as we beseech “you” (the “you” here is implied, not being in the Greek text; the implied object is general: everyone, everywhere) to be reconciled to God (5:20). 2 Corinthians 5:20 is the summation of Paul’s description of the Apostolic ministry. 2 Corinthians 5:21 is the summary explanation of the nature and source of this ministry: God made the sinless Messiah to bear the (Deuteronomic) curse of sin, so that we, in him, might embody (cf. 4:10), to you, God’s covenant faithfulness; i.e., righteousness, i.e., the faithfulness of Christ Jesus to the point of death, even death upon a Cross (cf. Galatians 3:13-14).
End summary. Now *that* is a powerful statement (by Paul) and restatement (by Wright) of the Apostolic ministry.