The tongue of the wise is health.
Healthy and unhealthy speech
Some men pride themselves on the pungency of their speech. They delight in sharp answers, keen retorts, quick repartees, and boast themselves when they cut their opponents in two. There are others who are gifted in the expression of complaint, reproach, and criticism against the whole providence of life. They can say sharp and bitter things about God and man, and they can be satisfied because of the edge of their own epigram, no matter against whom or against what that edge is directed. The tongue of the wise man is slower, but healthier; the wise man weighs his words: he is anxious to be associated only with judgments that can be confirmed by experience and illustrated by wisdom. The wise man speaks healthily--that is to say, he speaks out of the abundance of his own health, and he speaks in a way that will double and strengthen the health of others. To come near him is to ascend a mountain and breathe the freshest air of heaven, or to go down by the seashore and receive messages across the great deeps, full of vigour, and truth, and strengthening influence. Wise men keep society healthy. But for their presence it would stagnate, and go from one degree of corruption to another until it became wholly pestilential. There are two speakers in the text, to the end of time there will probably be two speakers in the world--the critical speaker and the judicial speaker; the man all sharpness and the man all thankfulness. The business of Christian discipline is to tame the tongue, to chasten it, to teach it the speech of wisdom, and to instruct it as to the right time of utterance and the right time of silence. (J. Parker, D.D.)