Romans 3:10

As it is written:

"There is no one righteous, not even one;

(v10, NIV)

Paul has just established that everybody is under sin. He begins to backup his argument by presenting support from the Old Testament. The first quote is from Psalms 14. This is only the beginning of the quote, but it begins by saying that no one is righteous. By saying no one is righteous; some may try to make an exception for themselves. However, it even says "not even one", in case any would try to object or point out an exception. Nobody is righteous and we see from this psalm of David how this point was made clear even in the Old Testament. No one is righteous, all are under sin.