פירוש על שמות 10:21

וימש חשך signifies and it (the darkness mentioned in the preceding phrase, ויהי חשך) shall darken for them the natural darkness to a higher degree than the darkness of night: i. e. the darkness of night shall become even more black and dark.

וימש חשך, same as ויאמש חשך. This construction with variable spelling is similar to Isaiah 13,20 ולא יהל שם ערבי meaning the same as ולא יאהל שם ערבי, “no Arab shall pitch his tent there.” By remembering this missing letter א, we understand the meaning of the line as “the darkness of the (previous) night will continue and intensify so that there will be no light for three days.”

נטה ידך על השמים, “in the direction of the atmosphere referred to as “heaven.” We have explained this in connection with Genesis 1,7.