Job 21:28 - Ellicott's Commentary On The Whole Bible

Of the prince — i.e., of the generous, virtuous, princely man? — the antithesis to the wicked man. “Behold I know your thoughts, for ye say, How can we tell who is virtuous and who is wicked? and consequently we know not to which catalogue you belong.” They had all along been insinuating that, though he seemed to be righteous, he was really wicked.