A prudent man concealeth knowledge: but the heart of fools proclaimeth foolishness.
– Proverbs 12:23
The word for concealeth means to hide or cover. A couple of senses are covered here. The wise man stores up knowledge (Proverbs 10:14), and he measures out his words (Proverbs 10:19; 11:13; 15:2). The main thought of the proverb is restraint or control over the tongue exercised by the prudent. The contrast comes in the fool proclaiming, or crying out, foolishness. Talkativeness is a mark of a fool (Proverbs 15:2). Not only does a fool pour out foolishness, but he also proves himself to be a fool by doing so (Proverbs 13:16; Ecclesiastes 10:3).