Proverbs 12:23
"A prudent man concealeth knowledge: but the heart of fools proclaimeth foolishness."
Cross References (ranked by relevance)
Every prudent man dealeth with knowledge: but a fool layeth open his folly.
A talebearer revealeth secrets: but he that is of a faithful spirit concealeth the matter.
In the multitude of words there wanteth not sin: but he that refraineth his lips is wise.
The tongue of the wise useth knowledge aright: but the mouth of fools poureth out foolishness.
Wise men lay up knowledge: but the mouth of the foolish is near destruction.
Yea also, when he that is a fool walketh by the way, his wisdom faileth him, and he saith to every one that he is a fool.