"He that is slow to wrath is of great understanding: but he that is hasty of spirit exalteth folly." Proverbs 14:29 KJV
Matthew Henry's Commentary:
Note, 1. Meekness is wisdom. He rightly understands himself, and his duty and interest, the infirmities of human nature, and the constitution of human society, who is slow to anger, and knows how to excuse the faults of others as well as his own, how to adjourn his resentments, and moderate them, so as by no provocation to be put out of the possession of his own soul. A mild patient man is really to be accounted an intelligent man, one that learns of christ, who is Wisdom itself.
Note, 2. Unbridled passion is folly proclaimed: He that is hasty of spirit, whose heart is tinder to every spark of provocation, that is all fire and tow, as we say, he thinks hereby to magnify himself and make those about stand in awe of him, whereas really he exalts his own folly; he makes it known, as that which is lifted up is visible to all, and he submits himself to it as the government of one that is exalted.