Exodus 10:21-26

Then the LORD told Moses, “Raise your hand toward the sky, and darkness will cover the land of Egypt. It will be so dark you will be able to feel it.” Moses raised his hand toward the sky, and total darkness was everywhere in Egypt for three days. No one could see anyone else, and no one could go anywhere for three days. But the Israelites had light where they lived. Again the king of Egypt called for Moses. He said, “All of you may go and worship the LORD. You may take your women and children with you, but you must leave your flocks and herds here.” Moses said, “You must let us have animals to use as sacrifices and burnt offerings, because we have to offer them to the LORD our God. So we must take our animals with us; not a hoof will be left behind. We have to use some of the animals to worship the LORD our God. We won’t know exactly what we will need to worship the LORD until we get there.”