Exodus 8:20-24

20The Lord said to Moses, “Get up early in the morning and position yourself before Pharaoh as he goes out to the water, and tell him, ‘Thus says the Lord, “Release my people that they may serve me!

21If you do not release my people, then I am going to send swarms of flies on you and on your servants and on your people and in your houses. The houses of the Egyptians will be full of flies, and even the ground they stand on.

22But on that day I will mark off the land of Goshen, where my people are staying, so that no swarms of flies will be there, that you may know that I am the Lord in the midst of this land.

23I will put a division between my people and your people. This sign will take place tomorrow.”’”

24The Lord did so; a thick swarm of flies came into Pharaoh’s house and into the houses of his servants, and throughout the whole land of Egypt the land was ruined because of the swarms of flies.