Matthew 6:19

The word "σής" (sēs) has a Hebrew origin: Hebrew סָס, sas Isaiah 51:8 see Strongs #5580.

Primary Meaning: Moth.

• Example: "[χρυσὸν] οὐ σ. οὐδὲ κὶς δάπτει" (Gold neither moth nor rust consumes) - Pindar.
• Also found in Aristophanes, Strabo, Matthew 6:19, and Luke 12:33.

Metaphorical: Refers to "bookworms" or "grammarians."

• Example: "σῆτες ἀκανθοβάται" or "-λόγοι" (thorn-walkers or -speakers), referring to grammarians or bookworms in the Anthologia Palatina (Antiphanes, Philodemus).

It goes without saying that Jesus uses symbolic language. What is a moth? A bookworm that attacks books. See Logeion Greek for more info.