Death and life are in the power of the tongue,
And those who love it will eat its fruit. - Proverbs 18:21

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. Does a spring send forth fresh water and bitter from the same opening? Can a fig tree, my brethren, bear olives, or a grapevine bear figs? Thus no spring yields both salt water and fresh. - James 3:5-12

He who has knowledge spares his words,
And a man of understanding is of a calm spirit.
Even a fool is counted wise when he holds his peace;
When he shuts his lips, he is considered perceptive. - Proverbs 17:27-28

In the multitude of words sin is not lacking,
But he who restrains his lips is wise. - Proverbs 10:19

So then, my beloved brethren, let every man be swift to hear, slow to speak, slow to wrath; for the wrath of man does not produce the righteousness of God. - James 1:19-20

If anyone among you thinks he is religious, and does not bridle his tongue but deceives his own heart, this one’s religion is useless. - James 1:26

A time to tear,
And a time to sew;
A time to keep silence,
And a time to speak. - Ecclesiastes 3:7