Proverbs 17:27 in the World English Bible
He who spares his words has knowledge. He who is even tempered is a man of understanding.
Context
26 Also to punish the just is not good, nor to strike princes for equity.
27 He that hath knowledge spareth his words: and a man of understanding is of an excellent spirit.
28 Even a fool, when he holdeth his peace, is counted wise: and he that shutteth his lips is esteemed a man of understanding.