Mark 7:21-22
For from within, out of the heart of men, proceed evil thoughts, fornications, thefts, murders, adulteries,
Luke 6:45
"The good man out of the good treasure of his heart brings forth that which is good; and the evil, out of the evil treasure brings forth that which is evil; for out of the abundance of the heart does his mouth speak.
James 1:26
If anyone thinks that he is religious, while he bridles not his own tongue, but deceives his own heart, this man's religion is vain.
James 3:5-8
So also the tongue is a little member, and boasts great things. Behold, how small a fire kindles how great a forest!