Should a wise man - Referring to Job, and to his claims to be esteemed wise; see Job 12:3; Job 13:2, Job 13:6. The argument of Eliphaz here is, that the sentiments which Job had advanced were a sufficient refutation of his pretensions to wisdom. A wise man would not be guilty of “mere talk,” or of using language that conveyed no ideas.
Utter - literally, answer. It refers to the replies which Job had made to the arguments of his friends.
Vain knowledge - Margin, “Knowledge of wind.” So the Hebrew; see Job 6:26; Job 7:7. The “wind” is used to denote what is unsubstantial, vain, changing. Here it is used as an emblem of remarks which were vain, empty, and irrelevant.
And fill his belly - Fill his mind with unsubstantial arguments or sentiments - as little fitted for utility as the east wind is for food. The image is, “he fills himself with mere wind, and then blows it out under pretence of delivering the maxims of wisdom.”
With the east wind - The east wind was not only tempestuous and vehement, but sultry, and destructive to vegetation. It passed over vast deserts, and was characterized by great dryness and heat. It is used here to denote a manner of discourse that had in it nothing profitable.