Exodus 8:18-22

18Then the Egyptian magicians tried to use their magic to make gnats appear. But they could not do it. The gnats were on all the people and on all the animals.

19Then the magicians said to Pharaoh, ‘This is the work of God.’ But there was no change in Pharaoh's thoughts. He would not listen to them. The Lord had said that this would happen, and it did!

20Then the Lord said to Moses, ‘Get up early in the morning. Meet Pharaoh when he goes out to the river. Then say to him, “The Lord says: You must let my people go. Let them go to worship me.

21If you do not let my people go, I will send thousands of flies on you. I will send them on your servants and on your people. I will send them into your houses. The houses of the Egyptians will be full of flies. The flies will cover all the ground where people live.

22But it will be different in the region of Goshen, where my people live. I will not send flies there. Then you will know that I, the Lord, am doing my work here in this land.