5:2

Your riches have rotted: In Bible times, a man’s wealth was measured not only in terms of his money​—his gold and silver​—but also in terms of the perishable goods that he possessed. Such goods might include livestock, grain, oil, wine, and clothing. (Ge 13:2; Job 1:3; Joe 2:19; Mt 11:8; Lu 12:16-19; see also Media Gallery, “The Clothing of the Rich and the Poor.”) All assets of that kind could perish, rot, or become spoiled. In this verse, James does more than emphasize how transitory such riches are; he also shows how worthless they can be if not used in the right way. He warns the rich that it is foolish to hoard earthly treasures and to trust in them. (Pr 11:28) Jesus made a similar point in his Sermon on the Mount, encouraging his followers to store up “treasures in heaven.” (Mt 6:19, 20) Here and in verse 3, James makes his point even more emphatic by describing events as if they had already taken place. He says “have rotted,” “has become,” and “have rusted away,” thus suggesting that the riches of such greedy people had already failed them.