[20] But the LORD hardened Pharaoh's heart, so that he would not let the children of Israel go. [21] And the LORD said unto Moses, Stretch out thine hand toward heaven, that there may be darkness over the land of Egypt, even darkness which may be felt. [22] And Moses stretched forth his hand toward heaven; and there was a thick darkness in all the land of Egypt three days: [23] They saw not one another, neither rose any from his place for three days: but all the children of Israel had light in their dwellings.