Proverbs 17:27-28

Amplified Bible

²⁷ 
He who has knowledge restrains and is careful with his words,
And a man of understanding and wisdom has a cool spirit (self-control, an even temper).^(A)
28 
Even a [callous, arrogant] fool, when he keeps silent, is considered wise;
When he closes his lips he is regarded as sensible (prudent, discreet) and a man of understanding.