The Egyptian astrologers had matched the first two plagues. Blood — yes. Frogs — yes. Lice — no. Targum Pseudo-Jonathan on Exodus 8:14 is blunt: The astrologers wrought with their burnings to bring forth the insects, but were not able.
Why did they fail here when they succeeded before? The tradition preserved in the Talmud and rehearsed by the meturgeman's contemporaries is that demons and magical forces can manipulate objects larger than a barley grain, but lice are smaller than that threshold. Magic has a floor. Below a certain size, only the Creator works.
Whether or not one accepts the technical explanation, the spiritual point is stunning. Empires can fake big miracles. They can stage the rivers, they can multiply frogs. What they cannot fake is the detail work — the tiny, intricate, living craftsmanship of creation itself. A single louse undoes Egypt's sorcerers because it requires the patience of a God who cares about microscopic life.
The Torah says the magicians finally confessed, this is the finger of God (Exodus 8:15). That confession was born not from a collapse of power, but from a collapse of pretense. The meturgeman's term their burnings — their ritual fires — simply would not ignite a louse.
The takeaway: the real test of divinity is not in the flashy miracle but in the small ones. A God who can make lice is a God who also made you.