Exodus 10:21-23

21And Jehovah said to Moses, Stretch out thy hand toward the heavens, that there may be darkness in the land of Egypt — so that one may feel darkness.

22And Moses stretched out his hand toward the heavens; and there was a thick darkness throughout the land of Egypt three days:

23they saw not one another, neither rose any from his place, for three days. But all the children of Israel had light in their dwellings.