Paul has argued that there are real benefits and privileges to being Jewish and the heritage that brings. However, does that actually benefit the Jews? Paul says “no” because Jews and Greeks, in other words, the representative Gentiles, alike sin (v9).
He then cites a number of Scripture passages, primarily from the Psalms to demonstrate this. First, he uses Psalms 14:1-3 and 53:1-3 to show that everyone is unrighteous and no one is good. Righteousness is specifically linked to seeking after God. Indeed, the Psalms link rejection of God to foolishness, so that we all lack wisdom. Instead of following God as he leads, we turn away. Note the link to Isaiah’s description of wandering sheep. The result is that we are useless, we cannot serve our intended purpose as those who glorify God and steard his creation. Again, there are further links here. We might think of Jeremiah’s vision of the potter at work and this will of course come up again in Romans 9-11 (v10-12).
Psalms 5:9 and 10:7 link unrighteousness to what we say as well as what we do. “Their talk is foul”, you might say that “their breath stinks” and it is the stench of death. What they say is poisonous (v13-14).
Isaiha 59:7-8 points to destructive actions. “They rush to murder” may point to an example of destructive and evil actions committed by some or may pick up on the idea that our words themselves end up being like snake venom. We may not physically murder but we can end up assassinating reputations and killing relationships (v15-17). Psalm36:1 reminds us in conclusion that the problem is our lack of fear or reverence to the Lord (v18).
So, this brings us back to the intent and effect of the Law. It applies first and foremost to its recipients, it convicts those who know but do not keep the Law of their sin but by showing what righteousness looks like, the Law also highlights the sinfulness of all people (v19). Paul finishes this thought on a pessimistic note, the Law is unable to make us right with God, all it can do is highlight our sin (v20).