Exodus 8:24

20The LORD said to Moses, “Rise up early in the morning, and stand before Pharaoh; behold, he comes out to the water; and tell him, ‘This is what the LORD says, “Let my people go, that they may serve me.

21Else, if you will not let my people go, behold, I will send swarms of flies on you, and on your servants, and on your people, and into your houses. The houses of the Egyptians shall be full of swarms of flies, and also the ground they are on.

22I will set apart in that day the land of Goshen, in which my people dwell, that no swarms of flies shall be there, to the end you may know that I am the LORD on the earth.

23I will put a division between my people and your people. This sign shall happen by tomorrow.”’”

24The LORD did so; and there came grievous swarms of flies into the house of Pharaoh, and into his servants’ houses. In all the land of Egypt the land was corrupted by reason of the swarms of flies.

25Pharaoh called for Moses and for Aaron, and said, “Go, sacrifice to your God in the land!”

26Moses said, “It isn’t appropriate to do so; for we shall sacrifice the abomination of the Egyptians to the LORD our God. Behold, if we sacrifice the abomination of the Egyptians before their eyes, won’t they stone us?

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

28Pharaoh said, “I will let you go, that you may sacrifice to the LORD your God in the wilderness, only you shall not go very far away. Pray for me.”