Do words matter? Do words reveal something about our heart? Do the words we speak possibly indicate something about the need for a change in behavior?
Jesus said in Matthew 12:34-37,
“You brood of vipers! how can you speak good, when you are evil? For out of the abundance of the heart the mouth speaks. The good man out of his good treasure brings forth good, and the evil man out of his evil treasure brings forth evil. I tell you, on the day of judgment men will render account for every careless word they utter; for by your words you will be justified, and by your words you will be condemned.”
Jesus explains further in Matthew 15:18-20
“… what comes out of the mouth proceeds from the heart, and this defiles a man. For out of the heart come evil thoughts, murder, adultery, fornication, theft, false witness, slander. These are what defile a man;”
Concerning truth and lies, Jesus said in John 8:44:
You are of your father the devil, and your will is to do your father’s desires. He was a murderer from the beginning, and has nothing to do with the truth, because there is no truth in him. When he lies, he speaks according to his own nature, for he is a liar and the father of lies.
In 2 Corinthians 12:20-21, Paul also implies a connection between sinful speech and unrepentant behavior.
For I fear that perhaps I may come and find you not what I wish, and that you may find me not what you wish; that perhaps there may be quarreling, jealousy, anger, selfishness, slander, gossip, conceit, and disorder. I fear that when I come again my God may humble me before you, and I may have to mourn over many of those who sinned before and have not repented of the impurity, immorality, and licentiousness which they have practiced.
James 3:6-8 says:
And the tongue is a fire. The tongue is an unrighteous world among our members, staining the whole body, setting on fire the cycle of nature, 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 humankind, but no human being can tame the tongue–a restless evil, full of deadly poison.
…if you have bitter jealousy and selfish ambition in your hearts, do not boast and be false to the truth. This wisdom is not such as comes down from above, but is earthly, unspiritual, devilish. For where jealousy and selfish ambition exist, there will be disorder and every vile practice.
But the wisdom from above is first pure, then peaceable, gentle, open to reason, full of mercy and good fruits, without uncertainty or insincerity.