"Their throat is an open sepulcher; with their tongues they have used deceit; the poison of asps is under their lips." (Romans 3:13)
In "Biblical Perspective" Gordon Snider writes concerning Romans 3:13:
The first two clauses here come from Psalm 5:9. Having shown that all men are affected by sin, Paul sought to show the extent of the damage. To do that, Paul listed six body parts that are affected. The three body parts mentioned in this verse — the throat, the tongue, and the lips — are each a part of the speech process. The speech of the ungodly corrupts those around him, defrauds those around him, and hurts and/or destroys. The last clause is from Psalm 140:3.
Source: Studies in the Psalms: Adult Teacher's Insights, page 11.