They make their tongues as sharp as a serpent's; the poison of vipers is on their lips. (NIV)
They sharpen their tongues like a serpent's; adders' poison is under their lips. Selah [pause, and calmly think of that]! [Rom. 3:13.] (AMP)
They have sharpened their tongues like a serpent; adders' poison is under their lips. Selah. (KJV)