Why does it say "El ha'Raki'a"?
Radak: This is like Al ha'Raki'a. Also "El he'Harim Lo Achal" (18:6, is like Al he'Harim) and many similar verses.
Which Keruvim are these?
Rashi: They are the four Chayos of the Merkavah. This Parashah calls them Keruvim, for the face of the ox turned into a Keruv, like it says below (verse 14). Yechezkel requested mercy - can a prosecutor (an ox, due to Chet ha'Egel) become an advocate?! Hashem changed it to a Keruv (Chagigah 13b).
Radak: They are the Chayos of Yechezkel's first vision, like it says "va'Eda Ki Cheruvim Hemah" (20).
What is the significance of seeing the Kisei?
Malbim: It is as if Hashem sat on the throne of mercy to lighten their punishment a little, via Yechezkel's advocation, and a remnant will remain. Based on the conduct of the Ofanim, which are the world of the Galgalim, Ma'arachah and nature, it was proper that all of them fall to the sword. Then, He would not burn the city and Mikdash, just He would kill all of them amidst His fury. Hashem changed Nebuchadnetzar's choice, to burn the city and leave a remnant of the nation under Gedalyah, and some will be exiled. He will not kill all of them. [Hashem] finished His anger on wood and stones. This was a matter of Hashgachah, not of the Ma'arachah. Therefore, it came from Olam ha'Kisei, which is above the Ofanim's conduct.
