Ecclesiastes 7:20
18 It is best to take hold of one warning without letting go of the other warning; for the one who fears God will follow both warnings. 19 Wisdom gives a wise person more protection than ten rulers in a city. 20 For there is not one truly righteous person on the earth who continually does good and never sins. 21 Also, do not pay attention to everything that people say; otherwise, you might even hear your servant cursing you. 22 For you know in your own heart that you also have cursed others many times.
Romans 3:10
8 And why not say, “Let us do evil so that good may come of it”?—as some who slander us allege that we say. (Their condemnation is deserved!) 9 What then? Are we better off? Certainly not, for we have already charged that Jews and Greeks alike are all under sin, 10 just as it is written: “There is no one righteous, not even one; 11 there is no one who understands; there is no one who seeks God. 12 All have turned away; together they have become worthless; there is no one who shows kindness, not even one.”
Notes and References
"... Before Paul establishes the full scope of the gospel, he addresses the problem of the extent of sin. He turns primarily to the Psalms, in the longest concatenation of Old Testament references in all his letters. His opening line is a bold asseveration: “No one is righteous, no, not one”. The quotation is almost certainly from the last line of Psalm 14:1: “There is none who does good”. The Septuagint, however, has translated the Hebrew ('there is no one doing good') with ('there is no one practicing kindness, not even one'). Paul’s rendering in Romans 3:10 is ('there is no one righteous, there is not even one'). Potentially, Paul was influenced by Ecclesiastes 7:20 ('Surely there is not a righteous man on earth'). The reason for Paul’s variation from both the Septuagint and from the MT is not clear ..."
Gibb, Ian Paul and the Psalms: Paul's Hermeneutic and Worldview (p. 152) University of Glasgow, 2017