John Gill's Exposition of the Whole Bible
Proverbs 17:20
He that hath a froward heart findeth no good,.... Who is of a perverse spirit, meditates and devises evil things; is not ingenuous and sincere, but false and deceitful to God and men: such an one gets no good from either; he obtains not the favour of God, nor a good name, credit, and reputation among men;
and he that hath a perverse tongue falleth into mischief; or "that turns himself", or "is turned in his tongue" w; whose tongue is changeable, as the Septuagint and Arabic versions; who sometimes says one thing, and sometimes another, and is not consistent with himself; as well as is contrary to all men: sooner or later he falls into mischief, into a pit, which he himself has dug for others; see James 3:6.
w ונהפך בלשונו "qui verterit se", Pagninus; "et verteus se in lingua sua", Montanus; "qui vertitur in lingua sua". Mercerus, Gejerus.