Albert Barnes on James 5:2

Your riches are corrupted. The word here rendered corrupted (σηπω) does not occur elsewhere in the New Testament. It means, to cause to rot, to corrupt, to destroy. The reference here is to their hoarded treasures; and the idea is, that they had accumulated more than they needed for their own use; and that, instead of distributing them to do good to others, or employing them in any useful way, they kept them until they rotted or spoiled. It is to be remembered, that a considerable part of the treasures which a man in the East would lay up, consisted of perishable materials, as garments, grain, oil, etc. Such articles of property were often stored up, expecting that they would furnish a supply for many years, in case of the prevalence of famine or wars. Compare Lk 12:18-19. A suitable provision for the time to come cannot be forbidden; but the reference here is to cases in which great quantities had been laid up, perhaps while the poor were suffering, and which were kept until they became worthless.

Your garments are moth-eaten. The same idea substantially is expressed here in another form. As the fashions in the East did not change as they do with us, wealth consisted much in the garments that were laid up for show or for future use. Mt 6:19. Q. Curtius says that when Alexander the Great was going to take Persepolis, the riches of all Asia were gathered there together, which consisted not only of a great abundance of gold and silver, but also of garments, Lib. vi. c. 5. Horace tells us that when Lucullus the Roman was asked if he could lend a hundred garments for the theatre, he replied that he had five thousand in his house, of which they were welcome to take part or all. Of course, such property would be liable to be moth-eaten; and the idea here is, that they had amassed a great amount of this kind of property which was useless to them, and which they kept until it became destroyed.

(a) "Your riches are corrupted" Jer 17:11 (b) "your garments are moth-eaten" Job 13:28