The Greek noun sēs (σής) means a moth — the insect known for consuming wool, clothing, and stored textiles. It appears only 3 times in the New Testament. In the ancient world, fine clothing was a significant form of stored wealth, and moth damage was a real economic threat. The moth thus became a natural metaphor for the silent, invisible destruction of earthly treasure.
Jesus uses sēs (moth) as part of his teaching on wealth, treasure, and the heart in the Sermon on the Mount (Matthew 6:19–21). 'Do not store up for yourselves treasures on earth, where moths (ses) and vermin destroy.' The image is of wealth that appears secure but is being silently consumed. James 5:2 employs the same imagery against the rich who have oppressed workers. The theological point is the inherent instability of earthly treasure — not that wealth is inherently evil, but that it is an unreliable security. Only treasure in heaven — which no moth can touch — constitutes genuine security. This teaching forces the question: where is your real trust invested?