Your riches. The meaning may be twofold: -- that he ridicules their foolish confidence, because the riches in which they placed their happiness, were wholly fading, yea, that they could be reduced to nothing by one blast from God -- or that he condemns as their insatiable avarice, because they heaped together wealth only for this, that they might perish without any benefit. This latter meaning is the most suitable. It is, indeed, true that those rich men are insane who glory in things so fading as garments, gold, silver, and such things, since it is nothing else than to make their glory subject to rust and moths; and well known is that saying "What is ill got is soon lost;" because the curse of God consumes it all, for it is not right that the ungodly or their heirs should enjoy riches which they have snatched, as it were, by violence from the hand of God. But as James enumerates the vices of which the rich brought on themselves the calamity which he mentions, the context requires, as I think, that we should say, that what he condemns here is the extreme rapacity of the rich, in retaining everything they could lay hold on, that it might rot uselessly in their chests. For thus it was, that what God had created for the use of men, they destroyed, as though they were the enemies of mankind. [1] But it must be observed, that the vices which he mentions here do not belong to all the rich; for some of them indulge themselves in luxury, some spend much in show and display, and some pinch themselves, and live miserably in their own filth. Let us, then, know that he here reproves some vices in some, and some vices in others. However, all those are generally condemned who unjustly accumulate riches, or who foolishly abuse them. But what James now says, is not only suitable to the rich of extreme tenacity, (such as Euclio of Plautus,) but to those also who delight in pomp and luxury, and yet prefer to heap up riches rather than to employ them for necessary purposes. For such is the malignity of some, that they grudge to others the common sun and air.

Footnotes

1 - Reference is made here to three sorts of riches, -- stores of corn, which rotted, -- garments, which were moth-eaten, -- and precious metals, money, and jewels, etc., which rusted.

Your riches are corrupted - The word here rendered "corrupted" (σήπω sēpō) 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 Luke 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. See the notes at Matthew 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 theater, 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.

Your riches are corrupted - Σεσηπε· Are putrefied. The term πλουτος, riches, is to be taken here, not for gold, silver, or precious stones, (for these could not putrefy), but for the produce of the fields and flocks, the different stores of grain, wine, and oil, which they had laid up in their granaries, and the various changes of raiment which they had amassed in their wardrobes.

Your riches are corrupted,.... Either through disuse of them; and so the phrase is expressive of their tenaciousness, withholding that from themselves and others which is meet, and which is keeping riches for the owners thereof, to their hurt; or these are corrupted, and are corruptible things, fading and perishing, and will stand in no stead in the day of wrath, and therefore it is great weakness to put any trust and confidence in them:
and your garments are moth eaten; being neither wore by themselves, nor put upon the backs of others, as they should, but laid up in wardrobes, or in chests and coffers, and so became the repast of moths, and now good for nothing.

corrupted--about to be destroyed through God's curse on your oppression, whereby your riches are accumulated (James 5:4). CALVIN thinks the sense is, Your riches perish without being of any use either to others or even to yourselves, for instance, your garments which are moth-eaten in your chests.
garments . . . moth-eaten--referring to Matthew 6:19-20.

The riches of the ancients consisted much in large stores of corn, and of costly apparel.