Exodus 8:16-19

16Then the Lord said to Moses, "Say to Aaron, 'Stretch out your staff and strike the dust of the earth, so that it may become gnats in all the land of Egypt.'"

17And they did so. Aaron stretched out his hand with his staff and struck the dust of the earth, and there were gnats on man and beast. All the dust of the earth became gnats in all the land of Egypt.

18The magicians tried by their secret arts to produce gnats, but they could not. So there were gnats on man and beast.

19Then the magicians said to Pharaoh, "This is the finger of God." But Pharaoh's heart was hardened, and he would not listen to them, as the Lord had said.