Paul develops his “all…under the power of sin” theme through a series of OT quotations: “Vv.10-12: Pss 14.1-2; 53.1-2. 13: Pss 5.9; 140.3. 14: Ps 10.7. 15-17: Isa 59.7-8; Prov 1.16. 18: Ps 36.1” (New Oxford Annotated Bible). I am puzzled by the series, since all the citations except Isa 59:7-8 are descriptions offered by one group of another group, hardly intended to cover the speakers. But perhaps this is Paul’s polemical point, that our eloquent denunciations of others tend to boomerang?
(Verses 10-18 might be useful in preparing for the confession and absolution portion of our worship, since multiple issues highlighted there reappear as issues for Christian communities in the epistles, e.g., kindness (v.12, cf. Col 3:12), the tongue (vv.13-14, cf. Jas 3:1-12), peace (v.17, cf. 2 Cor 13:11).
All “under the power of sin” implies that what’s needed is not simply repentance, but rescue. So it might set the stage for God’s intervention as a sort of new Exodus. But that is in the text’s future, with the present portrayed by the text simply bleak. This would be an unfortunate place for the book to end.
Paul caps his argument citing Psalm 143:2, and in its own way that psalm points the way forward in two respects. First, the opening petition highlights the Lord’s righteousness as the motive for the Lord’s non-judgmental intervention:
Hear my prayer, O LORD;
give ear to my supplications in your faithfulness;
answer me in your righteousness.
Do not enter into judgment with your servant,
for no one living is righteous before you. (Vv.1-2; see also v.11)
So in Paul it’s the Lord’s righteousness (dikaiosunē) that drives the Lord’s saving action.
Second, later in the petitions:
Teach me to do your will,
for you are my God.
Let your good spirit lead me
on a level path. (v.10)
So in Paul it’s the Holy Spirit that leads those incorporated in the Messiah.