RUST (חֶלְאָה, H2689, rust or scum; ἰός, G2675, rust). Rust speaks of oxidation, corrosion, or tarnishing of metal surfaces. In the Biblical references, rust has symbolical connotations. The thick rust in a cooking pot of bronze became symbolic of the unpurged wickedness of the inhabitants of Jerusalem in Ezekiel’s parable (24:6-13). In two NT passages a similar type of indictment is charged against those who accumulate wealth under the symbolism of the rusting of silver and gold (Matt 6:19, 20; James 5:3). In both cases the question arises whether the rust testifies to the impermanence of the wealth or whether it witnesses against the rich who prefer to hoard the wealth and let it rot rather than use it for benefiting others. The latter may better suit the context where in the apocalyptic imagery rust is almost a living avenging force (TDNT, III, p. 335).
International Standard Bible Encyclopedia (1915)
Strictly speaking rust is the red oxide of iron formed by the corrosion of that metal, but by extension it has come to mean corrosion produced on any metal. Chel’ah is translated "rust" in Eze 24:11,12. This rendering is probably based on 24:11. Copper caldrons are still used in Bible lands. Such vessels must be constantly watched when on the fire to guard against the possibility of their becoming dry. If this should happen the contents, whatever they may be, and the vessel itself will be injured. The copper of the caldron oxidizes and scales off in black or brownish scales, or rust. ios, was used in Greek to denote the corroding of metals. In Jas 5:3 occurs, "Your gold and your silver are rusted; and their rust .... shall eat your flesh as fire." The writers must have had in mind the actions of chemicals upon these metals which formed some such compound as the caustic silver nitrate.
Brosis, literally, "eating," which occurs in Mt 6:19,20, may refer to the diseases which attack such vegetation as wheat, grapes, cucumbers, etc. In no country is the saying "where moth and rust consume" (Mt 6:19) more true than in Syria. Any metal subject to corrosion seems to rust faster in that country than anywhere else. There are also many rusting fungi which the people have not learned to destroy and which do much damage to the crops.
See also SCUM.
James A. Patch