“The Lord said to Moses: Extend your hand toward the heavens, and there will be darkness over the land of Egypt, and the darkness will be tangible” (Exodus 10:21). “The Lord said to Moses: Extend your hand toward the heavens.” That is what is written: “He sent darkness, and it was dark; and they did not defy [maru] His word” (Psalms 105:28). Our Rabbis said: It is because they did not accept the authority [marut] of the word of the Holy One blessed be He over them.
Alternatively, the Holy One blessed be He said to the angels: ‘The Egyptians deserve to be afflicted with darkness,’ and they all immediately agreed as one, and did not defy. What is: “He sent darkness, and it was dark”? To what is this matter similar? It is similar to a master whose servant sinned against him.
He said to someone: ‘Go and strike him fifty beatings.’ He went and struck him one hundred beatings, adding some of his own. So, the exalted Holy One blessed be He sent darkness upon the Egyptians, and the darkness added on its own; that is: “He sent darkness, and it was dark [vayaḥshikh].”1This could be translated as “and it made it dark.” “And the darkness will be tangible.”
What were the dimensions of the darkness? Our Rabbis said: It was as thick as a dinar,2A coin. as it is stated: “And the darkness will be tangible [veyamesh],” that it had substance [mamash].