Proverbs 16:27-30 (ESV)

27 A worthless man plots evil,
and his speech is like a scorching fire.
28 A dishonest man spreads strife,
and a whisperer separates close friends.
29 A man of violence entices his neighbor
and leads him in a way that is not good.
30 Whoever winks his eyes plans dishonest things;
he who purses his lips brings evil to pass.

 

James 3:6-9 (ESV)

And the tongue is a fire, a world of unrighteousness. The tongue is set among our members, staining the whole body, setting on fire the entire course of life, and set on fire by hell. For every kind of beast and bird, of reptile and sea creature, can be tamed and has been tamed by mankind, but no human being can tame the tongue. It is a restless evil, full of deadly poison. With it we bless our Lord and Father, and with it we curse people who are made in the likeness of God.