The Prophet refers here to the king of Babylon and all his people. He will change, he says, his spirit; that is, success will take away from him whatever reason and moderation he had. Now since the proud betray themselves and their disposition when fortune smiles on them, let us learn to form our judgement of men according to this experiment. If we would judge rightly of any man we must see how he bears good and bad fortune; for it may be that he who has borne adversity with a patient, calm and resigned mind, will disappoint us in prosperity, and will so elate himself as to be wholly another man. The Prophet then does not without reason speak of a change of spirit; for though the Chaldeans were before proud, they were not so extremely haughty as when their pride passed all bounds, after their many victories. He will change then his spirit; not that the Chaldeans were another kind of people, but that the Lord thus discovered their madness which was before hid.