Exodus 8:21-24

21Or else, if you will not let My people go, behold, I will send swarms of flies on you and your servants, on your people and into your houses. The houses of the Egyptians shall be full of swarms of flies, and also the ground on which they stand.

22And in that day I will set apart the land of Goshen, in which My people dwell, that no swarms of flies shall be there, in order that you may know that I am the Lord in the midst of the land.

23I will make a difference between My people and your people. Tomorrow this sign shall be.” ’ ”

24And the Lord did so. Thick swarms of flies came into the house of Pharaoh, into his servants’ houses, and into all the land of Egypt. The land was corrupted because of the swarms of flies.