Job 21:18 - Joseph Benson’s Commentary on the Old and New Testaments

They are as stubble before the wind, &c. That is, their destruction shall be speedy, certain, and irrecoverable. Thus he goes on to concede to his adversaries, “that wicked men are sometimes thus severely punished, as they in their speeches had been fond of representing; but then he had before shown, that they were sometimes as remarkably prosperous; and this made way for a third particular, which is indeed his general assertion all along, and the medium by which he endeavoured to convince them of the rashness of their censures and suspicions of him; namely, that things are dealt out here promiscuously, and without any strict regard to merit or demerit.” Dodd.