Exodus 8:21-24

If you don’t let them go, I will send swarms of flies into your houses. The flies will be on you, your officers, and your people. The houses of Egypt will be full of flies, and they will be all over the ground, too. But I will not treat the Israelites the same as the Egyptian people. There will not be any flies in the land of Goshen, where my people live. By this you will know that I, the LORD, am in this land. I will treat my people differently from your people. This miracle will happen tomorrow.’ ” So the LORD did as he had said, and great swarms of flies came into the king’s palace and his officers’ houses. All over Egypt flies were ruining the land.