Elihu is closing his argument on God being unable to be judged with a hypothetical. A man says that he has suffered greatly without a known cause, and asks what must change for this to stop. Of course, this mirrors Job's situation. Elihu is raising the point that we don't know exactly why God does everything so rather than relying on sinful human beings to set the terms for justice, we should rely on God who is Himself justice and knows all things. At the end, Elihu quotes the friends who outright condemn Job as sinful but do so also because they do not know the specifics and try to justify judgment on their terms, not God's.