Exodus 8:5, 17

Then the LORD said to Moses, “Tell Aaron, ‘Raise the staff in your hand over all the rivers, canals, and ponds of Egypt, and bring up frogs over all the land.’”

So Moses and Aaron did just as the LORD had commanded them. When Aaron raised his hand and struck the ground with his staff, gnats infested the entire land, covering the Egyptians and their animals. All the dust in the land of Egypt turned into gnats.