Why does the Torah write "ka'Es Machar" (and not just 'Machar', as it did for Makas Dever [See Pasuk 5])?
Rashi: Moshe made a niche on the wall, and said to Pharaoh that the following day, when the sun reaches that niche, the hail will begin to fall. 1
See Sifsei Chachamim. If the hail began to fall in all of Egypt at that moment, the sky should have been full of clouds. It is an added wonder that the sun shone! (PF)
Why does the Torah add "b'Mitzrayim" (See also Pasuk 24)?
Ramban: This suggests that there were plagues of hail that were just as heavy as this one, 1 and it is only in Egypt, where it never rains, and where hail was a mind-boggling phenomenon, that the plague was unique. 2
The current Pesukim relate what Hashem instructed Moshe to say to Pharaoh. Why does the Torah not inform us that Moshe passed on the message?