Read James 5:3 Using Other Translations
Your gold and silver is cankered; and the rust of them shall be a witness against you, and shall eat your flesh as it were fire. Ye have heaped treasure together for the last days.
Your gold and silver have corroded, and their corrosion will be evidence against you and will eat your flesh like fire. You have laid up treasure in the last days.
Your gold and silver are corroded. The very wealth you were counting on will eat away your flesh like fire. This corroded treasure you have hoarded will testify against you on the day of judgment.