Matthew Poole and continuators on Psalms 50:19

19. Thou givest thy mouth to evil , and thy tongue frameth deceit .

Heb. thou sendest forth, to wit free; for the Word is used of Mens dismissing their Wives, or their Servants; whom they left to their Freedom. Thou hast an unbridled Tongue, and castest off all restraints of God's law, and of thy own Conscience, and givest thy Tongue Liberty to speak what thou pleasest, though it be offensive and dishonourable to God, and injurious to thy Neighbour, or to thy own Soul. Which is justly produced as an Evidence of their Hypocrisie.

Either to sinful or Mischievous Speeches.

(i. e.) Uttereth Lyes or fair Words, wherewith to Circumvent those who deal with them.