So according to the Targumist, Haman is bid to go aklmd yzng tybl, "to the king's treasury", and take from thence one of the purple garments, the best, and raiment of the best silk, &c. and these were liable to be eaten with the moth, Jas 5:2.
The word translated rust, does not here signify the rust of metals, as gold and silver; by which there is not so much damage done, so as to destroy them, and make them useless; but whatever corrupts and consumes things eatable, as blasting and mildew in corn, or any sort of vermin in granaries: for gold and silver, or money, with jewels and precious stones, which make a very great part of worldly treasure, seem to be more particularly designed, by what thieves break through into houses for, and carry away.
So that here are three sorts of earthly treasures pointed at, which are liable to be corrupted, or taken away: garments, which may be destroyed, and rendered useless for wearing; provisions of things eatable, as all sorts of corn and grain, which may be so corrupted by smut and vermin, as not to be fit for use; and money and jewels, which may be stolen by thieves: so that no sort of worldly riches and treasure is safe, and to be depended on; and therefore it is a great folly and vanity to lay it up, and trust in it.
Targum Sheni. in Esth. vi.