Exodus 8:25-29

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

26But Moses replied, “It would not be right to do that, because the sacrifices we offer to the LORD our God would be detestable to the Egyptians. If we offer sacrifices that are detestable before the Egyptians, will they not stone us? 27We must make a three-day journey into the wilderness and sacrifice to the LORD our God as He commands us.”

28Pharaoh answered, “I will let you go and sacrifice to the LORD your God in the wilderness, but you must not go very far. Now pray for me.”

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