Exodus 8:24-27

24And the Lord did this. Thick swarms of flies went into Pharaoh’s palace and his officials’ houses. Throughout Egypt the land was ruined because of the swarms of flies.

25Then Pharaoh summoned Moses and Aaron and said, “Go sacrifice to your God within the country.”

26But Moses said, “It would not be right to do that, because what we will sacrifice to the Lord our God is detestable to the Egyptians. If we sacrifice what the Egyptians detest in front of them, won’t they stone us?

27We must go a distance of three days into the wilderness and sacrifice to the Lord our God as he instructs us.”