Great men are not always wise - Though wisdom may in general be looked for in them, yet it is not universally true. Great men here denote those who are distinguished for rank, age, authority.
Neither do the aged understand judgment - That is, they do not always understand it. The word judgment here means right, truth. They do not always understand what is the exact truth in regard to the divine administration. This is an apology for what he was about to say, and for the fact that one so young should speak. Of the truth of what he here said there could be no doubt, and hence, there was a propriety that one who was young should also be allowed to express his opinion on important subjects.

Great men are not always wise - This is a true saying, which the experience of every age and every country increasingly verifies. And it is most certain that, in the case before us, the aged did not understand judgment; they had a great many wise and good sayings, which they had collected, but showed neither wisdom nor discretion in applying them.

Great men are not always wise,.... Men of grandeur and dignity, as Job's friends might be, the rich, the honourable, and noble; the apostle is thought to refer to this, at least to express the sentiment contained in it, 1-Corinthians 1:26; or the great in quantity, the many, the multitude; and therefore are not to be followed in principle or practice; or that are great in years, well stricken in age, have lived long in the world, so some versions (q); or are doctors, teachers of others, masters in Israel, as Nicodemus, and yet ignorant; all these may be wise in natural, civil, and worldly things, though this is not always the case; but not wise and knowing in divine and spiritual things, particularly in those respecting the causes and reasons of God's providential dealings with men, afflicting the righteous, and suffering the wicked to prosper, which is more fully explained in the next clause:
neither do the aged understand judgment; what is right and wrong, the difference between truth and error, and particularly the judgments of God, which are unsearchable, and his ways past finding out; even so to understand them as to observe and acknowledge his sovereignty, wisdom, truth, and faithfulness in them.
(q) Sept. "longaevi", V. L. Mr. Broughton renders it, "as men of not great time may be wise, as the old understand the right."

Great--rather, "old" (Job 32:6). So Hebrew, in Genesis 25:23. "Greater, less" for the older, the younger.
judgment--what is right.

Judgment - What is just and right.