Exodus 10:21-26

And Jehovah said unto Moses, Stretch out thy hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt. And Moses stretched forth his hand toward heaven; and there was a thick darkness in all the land of Egypt three days; they saw not one another, neither rose any one from his place for three days: but all the children of Israel had light in their dwellings. And Pharaoh called unto Moses, and said, Go ye, serve Jehovah; only let your flocks and your herds be stayed: let your little ones also go with you. And Moses said, Thou must also give into our hand sacrifices and burnt-offerings, that we may sacrifice unto Jehovah our God. Our cattle also shall go with us; there shall not a hoof be left behind: for thereof must we take to serve Jehovah our God; and we know not with what we must serve Jehovah, until we come thither.