New Revised Standard Version
One who spares words is knowledgeable; one who is cool in spirit has understanding.

Contemporary English Version
It makes a lot of sense to be a person of few words and to stay calm.

New American Bible
Those who spare their words are truly knowledgeable, and those who are discreet are intelligent.

Douay-Rheims Bible
He that setteth bounds to his words, is knowing and wise: and the man of understanding is of a precious spirit.

He that setteth bounds to his words, is knowing and wise: and the man of understanding is of a precious spirit.

spareth

Proverbs 10:19 The tongue of the just is as choice silver: but the heart of the wicked is nothing worth.

Proverbs 15:28 The mind of the just studieth obedience: the mouth of the wicked overfloweth with evils.

James 1:19 You know, my dearest brethren. And let every man be swift to hear, but slow to speak and slow to anger.

James 3:2 For in many things we all offend. If any man offend not in word, the same is a perfect man. He is able also with a bridle to lead about the whole body.

an excellent spirit

Proverbs 16:32 The patient man is better than the valiant: and he that ruleth his spirit, than he that taketh cities.

Ecclesiastes 9:17 The words of the wise are heard in silence, more than the cry of a prince among fools.

James 3:18 And the fruit of justice is sown in peace, to them that make peace.