Malbim: Iyov does not sense that he caused his own punishment. He should have put to his heart. This is like "va'Telahatehu mi'Saviv v'Lo Yada va'Tiv'ar Bo v'Lo Yasim Al Lev." They plundered his property because he did not eradicate them from the land. They killed his children because he did not put to his heart to repent from his sin. The evil boils were due to indulging in excesses. Reward and punishment come from man's actions!