Exodus 8:24-27

24And the Lord did so; and there came a grievous swarm of flies into the house of Pharaoh, and into his servants’ houses, and into all the land of Egypt: the land was corrupted by reason of the swarm of flies.1

25And Pharaoh called for Moses and for Aaron, and said, Go ye, sacrifice to your God in the land. 26And Moses said, It is not meet so to do; for we shall sacrifice the abomination of the Egyptians to the Lord our God: lo, shall we sacrifice the abomination of the Egyptians before their eyes, and will they not stone us? 27We will go three days’ journey into the wilderness, and sacrifice to the Lord our God, as he shall command us.