Exodus 10:21-26

Then the LORD said to Moses, “Lift your hand toward heaven, and the land of Egypt will be covered with a darkness so thick you can feel it.” So Moses lifted his hand to the sky, and a deep darkness covered the entire land of Egypt for three days. During all that time the people could not see each other, and no one moved. But there was light as usual where the people of Israel lived. Finally, Pharaoh called for Moses. “Go and worship the LORD,” he said. “But leave your flocks and herds here. You may even take your little ones with you.” “No,” Moses said, “you must provide us with animals for sacrifices and burnt offerings to the LORD our God. All our livestock must go with us, too; not a hoof can be left behind. We must choose our sacrifices for the LORD our God from among these animals. And we won’t know how we are to worship the LORD until we get there.”