Exodus 8:25-29

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.”

28Pharaoh responded, “I will let you go and sacrifice to the Lord your God in the wilderness, but don’t go very far. Make an appeal for me.”

29“As soon as I leave you,” Moses said, “I will appeal to the Lord, and tomorrow the swarms of flies will depart from Pharaoh, his officials, and his people. But Pharaoh must not act deceptively again by refusing to let the people go and sacrifice to the Lord.”