On the night of the Exodus, God did not just strike the firstborn of Egypt. He also executed judgment on the gods of Egypt. And according to the Mekhilta, those judgments were not uniform — each idol was destroyed according to its material, in a way uniquely suited to humiliate it.
Images made of stone crumbled. Images made of wood rotted. Images made of metal rusted. Each material suffered its own form of decay, as if God were demonstrating mastery over every substance the Egyptians had fashioned into objects of worship. Stone, the most durable of materials, fell apart. Wood, which can last for centuries in Egypt's dry climate, decomposed overnight. Metal, resistant to corrosion, corroded before their eyes.
The proof text comes from Numbers: "And the Egyptians were burying those whom the Lord had smitten — every firstborn, and against their gods the Lord had executed judgments" (Numbers 33:4). The verse pairs the death of the firstborn with the destruction of the idols, placing them in the same night, the same act of divine reckoning.
An alternative tradition preserved in the Mekhilta reverses the deterioration patterns: stone idols rotted (experiencing the decay proper to organic material), while metal idols melted. The disagreement is significant. In the first version, each material suffers its natural form of destruction, accelerated beyond any natural timeline. In the second version, each material suffers an unnatural destruction — stone behaving like wood, metal behaving like wax — as if the laws of physics themselves bent to God's will. Either way, the message is the same: no material in the universe is strong enough to house a false god when the true God decides to act.