'Darkness' in the Bible

And 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.

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

And it came between the camp of the Egyptians and the camp of Israel; and was a cloud and darkness, and lit up the night; and the one did not come near the other all the night.

And Jehovah said to Moses, Lo, I will come to thee in the cloud's thick darkness, that the people may hear when I speak with thee, and believe thee also for ever. And Moses told the words of the people to Jehovah.