The iron that may not be lifted

Exodus 20:25 — "if thou lift up thy tool upon it, thou hast polluted it." Deuteronomy 27:5 — an altar of whole stones, "thou shalt not lift up any iron tool upon them." And then 1 Kings 6:7, describing the Temple going up: "there was neither hammer nor axe nor any tool of iron heard in the house, while it was in building."

The classical explanation is that iron shortens life while the altar lengthens it, so the one may not be raised against the other — the sword's metal has no business in the house of peace.

The consequence is the point. Forbid the hand's tool and something else has to do the cutting — so the tradition supplies a creature that cuts with its mouth. Same structure as Isaiah's worm and the cedar, arrived at from the opposite end: there, the mouth is all you have; here, the mouth is all you are allowed.