16 So the Lord said to Moses, "Tell Aaron, 'Raise your staff and strike the ground. The dust will turn into swarms of gnats throughout the land of Egypt.'" 17 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. 18 Pharaoh's magicians tried to do the same thing with their secret arts, but this time they failed. And the gnats covered everyone, people and animals alike.
Matthew Henry's Commentary on Exodus 8:16-18
Commentary on Exodus 8:16-19
(Read Exodus 8:16-19)
These lice were produced out of the dust of the earth; out of any part of the creation God can fetch a scourge, with which to correct those who rebel against him. Even the dust of the earth obeys him. These lice were very troublesome, as well as disgraceful to the Egyptians, whose priests were obliged to take much pains that no vermin ever should be found about them. All the plagues inflicted on the Egyptians, had reference to their national crimes, or were rendered particularly severe by their customs. The magicians attempted to imitate it, but they could not. It forced them to confess, This is the finger of God! The check and restraint put upon us, must needs be from a Divine power. Sooner or later God will force even his enemies to acknowledge his own power. Pharaoh, notwithstanding this, was more and more obstinate.