אלו עשה באלוהיהם, ולא הרג את־בכוריהם, דיינו “If God had judged their gods but had not killed their first born, it been enough for us!” If God had completely removed the idols of Egypt so that they no longer became impure from them, it would have been enough. But God also killed their firstborn because Egypt was considered firstborn among the constellations (mazalot). By killing the firstborn, everyone realized that it did not have power.