Exodus 8:20-32

Then the LORD said to Moses, “Get up early in the morning and confront Pharaoh as he goes to the river and say to him, ‘This is what the LORD says: Let my people go, so that they may worship me. If you do not let my people go, I will send swarms of flies on you and your officials, on your people and into your houses. The houses of the Egyptians will be full of flies; even the ground will be covered with them. “ ‘But on that day I will deal differently with the land of Goshen, where my people live; no swarms of flies will be there, so that you will know that I, the LORD, am in this land. I will make a distinction between my people and your people. This sign will occur tomorrow.’ ” And the LORD did this. Dense swarms of flies poured into Pharaoh’s palace and into the houses of his officials; throughout Egypt the land was ruined by the flies. Then Pharaoh summoned Moses and Aaron and said, “Go, sacrifice to your God here in the land.” But Moses said, “That would not be right. The sacrifices we offer the LORD our God would be detestable to the Egyptians. And if we offer sacrifices that are detestable in their eyes, will they not stone us? We must take a three-day journey into the wilderness to offer sacrifices to the LORD our God, as he commands us.” Pharaoh said, “I will let you go to offer sacrifices to the LORD your God in the wilderness, but you must not go very far. Now pray for me.” Moses answered, “As soon as I leave you, I will pray to the LORD, and tomorrow the flies will leave Pharaoh and his officials and his people. Only let Pharaoh be sure that he does not act deceitfully again by not letting the people go to offer sacrifices to the LORD.” Then Moses left Pharaoh and prayed to the LORD, and the LORD did what Moses asked. The flies left Pharaoh and his officials and his people; not a fly remained. But this time also Pharaoh hardened his heart and would not let the people go.