What is the meaning of "Albish Shamayim Kadrus"?
Radak #1: So I did in Egypt, when air was lost for them. I clothed Shamayim in darkness for them. They had darkness for three days. It mentions water and air 1 , for they are [among the four] 'elements'. Hashem does His will with the elements, and all the more so with what is created from them!
Radak #2: This refers to darkening the sun and moon, or the clouds - "veha'Shamayim Hiskadru Avim v'Ru'ach" (Melachim I, 18:45).
Malbim: The sea will not dry due to heat of the sun. Rather, I will clothe the sky with darkness (clouds).
The verse did not explicitly mention air! (PF)
How did Hashem make their garments Sak (sackcloth)?
Radak: It was as if their garments were Sak; they did not see light. Sak is black. If I did all this, I can take you out of Galus, even though you are amidst many nations.
Malbim: They will be full of thick clouds and rain, as if they are covered with Sak.
