Exodus 10:20-24

But the LORD hardened Pharaoh’s heart, so that he would not let the children of Israel go.

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.

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 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 the LORD; only let your flocks and your herds be stayed: let your little ones also go with you.