Matthew 12:34-37 Brood of vipers! How can you, being evil, speak good things? For out of the abundance of the heart the mouth speaks. A good man out of the good treasure of his heart brings forth good things, and an evil man out of the evil treasure brings forth evil things. But I say to you that for every idle word men may speak, they will give account of it in the day of judgment. For by your words you will be justified, and by your words you will be condemned."
Psalm 15:1-3 LORD, who may abide in Your tabernacle? Who may dwell in Your holy hill? He who walks uprightly, And works righteousness, And speaks the truth in his heart; He who does not backbite with his tongue, Nor does evil to his neighbor, Nor does he take up a reproach against his friend;
Proverbs 10:19 In the multitude of words sin is not lacking, But he who restrains his lips is wise.
Ecclesiastes 5:1-7 Walk prudently when you go to the house of God; and draw near to hear rather than to give the sacrifice of fools, for they do not know that they do evil. Do not be rash with your mouth, And let not your heart utter anything hastily before God. For God is in heaven, and you on earth; Therefore let your words be few. For a dream comes through much activity, And a fool's voice is known by his many words. When you make a vow to God, do not delay to pay it; For He has no pleasure in fools. Pay what you have vowed— Better not to vow than to vow and not pay. Do not let your mouth cause your flesh to sin, nor say before the messenger of God that it was an error. Why should God be angry at your excuse and destroy the work of your hands? For in the multitude of dreams and many words there is also vanity. But fear God.
Colossians 4:6 Let your speech always be with grace, seasoned with salt, that you may know how you ought to answer each one.
James 1:19 So then, my beloved brethren, let every man be swift to hear, slow to speak, slow to wrath;
James 3:2 For we all stumble in many things. If anyone does not stumble in word, he is a perfect man, able also to bridle the whole body.
James 3:4-10 Look also at ships: although they are so large and are driven by fierce winds, they are turned by a very small rudder wherever the pilot desires. Even so the tongue is a little member and boasts great things. See how great a forest a little fire kindles! And the tongue is a fire, a world of iniquity. The tongue is so set among our members that it defiles the whole body, and sets on fire the course of nature; and it is set on fire by hell. For every kind of beast and bird, of reptile and creature of the sea, is tamed and has been tamed by mankind. But no man can tame the tongue. It is an unruly evil, full of deadly poison. With it we bless our God and Father, and with it we curse men, who have been made in the similitude of God. Out of the same mouth proceed blessing and cursing. My brethren, these things ought not to be so.
John 8:44 You are of your father the devil, and the desires of your father you want to do. He was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he speaks a lie, he speaks from his own resources, for he is a liar and the father of it.
1 Peter 2:23 who, when He was reviled, did not revile in return; when He suffered, He did not threaten, but committed Himself to Him who judges righteously;
Galatians 6:7 Do not be deceived, God is not mocked; for whatever a man sows, that he will also reap.