Mark 7:21-22
For from within, out of the heart of men, come forth evil thoughts, fornications,
Luke 6:45
The good man out of the good treasure of his heart bringeth forth that which is good; and the evil man out of the evil treasure bringeth forth that which is evil; for out of the abundance of his heart his mouth speaketh.
James 1:26
If any one thinks that he is religious, and bridles not his tongue, but deceives his own heart, this mans religion is vain.
James 3:5-8
So also the tongue is a little member, and boasteth great things. Behold, how great a forest a little fire kindleth!