Of whom, what, why?
28 Even a fool, when he holds his peace, is counted wise: and he that shuts his lips is esteemed a man of understanding."
In other words, the man or woman of understanding knows when to keep his or her mouth shut. It is the wise person that knows when and where to stay silent because they know that the fool will eventually expose their lack of knowledge and understanding. It's also best to chose carefully your words when one does decide to speak.
Better to remain silent and be thought a fool than to speak and to remove all doubt.
— ABRAHAM LINCOLN.