In this passage, rather than separating Jews and Gentiles in their sinfulness as he has thus far, Paul simply says that both Jews and Gentiles are sinful, and therefore need righteousness. He begins by raising a possible response to his statement that the condemnation of those who have slandered him is just. This response is that Paul is better than them. Evidently, the ones who were slandering him were Gentiles because he makes this distinction in verse 9 when he says that he is not better than them because, as he has already stated, both Jews and Greeks are under sin, or condemned because of their sinfulness.
In verse 10, Paul begins to quote Scripture to prove that both Jews and Gentiles are under sin. The first reason that they are both under sin is that none of them is righteous. Secondly, none of them understands how to seek God. Thirdly, none of them seeks God. Fourthly, all of them have turned away from God. Fifthly, all of them have become useless. Sixthly, none of them does good. Seventhly, they speak things that result in death. Eighthly, they deceive people. Ninthly, they habitually and bitterly curse. Tenthly, they are quick to kill others. Also, they bring destruction and misery. In addition, they do not know how to make peace. Finally, they do not fear God. After quoting from Scripture, Paul immediately talks about the Law saying things. He says that the Law speaks to those who are obligated to obey it so that everyone can become accountable to God. The reason for this is that no one can be justified by God by the works of the Law, or obedience to it. That is not the purpose of the Law. Rather, the purpose of the Law is to give people knowledge about sin.