For thou hast hid their heart from understanding
That is, the hearts of his friends, and therefore they were unfit to undertake his cause, or be sureties for him, or be judges in it. It is the same thing as to hide understanding from their hearts, which God sometimes does in a natural sense; when men like not the knowledge of him, as attainable by the light of nature, he gives them up to reprobate minds, minds void of knowledge and judgment in things natural; and sometimes, in a spiritual sense, he hides men's hearts from the knowledge of things divine and evangelical, and even this he does from the wise and prudent of this world; yea, sometimes he hides the knowledge of his providential dealings with men from his own people, as he did from Asaph, Jeremiah, Habakkuk, and others; and, as it seems, from Job's friends, who therefore mistook his case, and were very unfit and insufficient to determine it:
therefore shalt thou not exalt [them];
to such honour and dignity, to be umpires, arbitrators, or judges in the case of Job; this God had reserved for another, Elihu, or rather himself, who decided the controversy between Job and his friends, and declared in his favour, and that they had not spoken the thing that was right of him, as his servant Job had done, ( Job 42:7 ) ;