He that hath knowledge spareth his words: and a man of understanding is of an excellent spirit. Even a fool, when he holdeth his peace, is counted wise: and he that shutteth his lips is esteemed a man of understanding” (Proverbs 17:27, 28).
Sometimes the best indication of a foolish person is when they open their mouth and begin to speak. Knowing when to speak and when to keep silent, and finding the right words to say, is part of godly wisdom. True knowledge, wisdom, and understanding are gifts from the Holy Spirit.