Exodus 8:22-26

But on that day I will set apart the land of Goshen, where My people are living, so that no swarms of flies will be there, in order that you may know that I, the Lord, am in the midst of the land.

I will put a division between My people and your people. Tomorrow this sign will occur.” ’ ”

Then the Lord did so. And thick swarms of flies entered the house of Pharaoh and the houses of his servants, and the land was laid waste because of the swarms of flies in all the land of Egypt.

Then Pharaoh called for Moses and Aaron and said, “Go, sacrifice to your God within the land.”

But Moses said, “It is not permissible for us to do so, because we will sacrifice to the Lord our God that which is an abomination to the Egyptians. If we sacrifice that which is an abomination to the Egyptians before their eyes, will they not stone us?