Proverbs 12:23 in the King James Version
A prudent man concealeth knowledge: but the heart of fools proclaimeth foolishness.
Context
22 Lying lips are an abomination to the LORD, but those who do the truth are his delight.
23 A prudent man keeps his knowledge, but the hearts of fools proclaim foolishness.
24 The hands of the diligent ones shall rule, but laziness ends in slave labor.