Exodus 8:17-19

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