Exodus 8:26

23 And I will put a division between my people and thy people: to morrow shall this sign be.

24 And 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.

25 And Pharaoh called for Moses and for Aaron, and said, Go ye, sacrifice to your God in the land.

26 And 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?

27 We will go three days' journey into the wilderness, and sacrifice to the LORD our God, as he shall command us.

28 And Pharaoh said, I will let you go, that ye may sacrifice to the LORD your God in the wilderness; only ye shall not go very far away: intreat for me.

29 And Moses said, Behold, I go out from thee, and I will intreat the LORD that the swarms of flies may depart from Pharaoh, from his servants, and from his people, to morrow: but let not Pharaoh deal deceitfully any more in not letting the people go to sacrifice to the LORD.