Exodus 8:25-27

Then Pharaoh called for Moses and Aaron and said, “Go, sacrifice to your God [here] in the land [of Egypt].” But Moses said, “It is not right [or even possible] to do that, for we will sacrifice to the LORD our God what is repulsive and unacceptable to the Egyptians [that is, animals that the Egyptians consider sacred]. If we sacrifice what is repulsive and unacceptable to the Egyptians, will they not riot and stone us? We must go a three days’ journey into the wilderness and sacrifice to the LORD our God as He commands us.”