What is "Ratzo va'Shov"?
Rashi citing Chagigah 13b: It is like a flame that constantly exudes from a furnace, and quickly returns. So they remove their heads from under the Raki'a spread above them, and are startled from the Shechinah and rush to return their heads.
Radak: The root of Ratzo is Ratzah (to want); the Aleph is in place of the Hei. It is like Merutzeh (pleased). Ratzah is like Rutz. Also "va'Tiretz Imo" (Tehilim 50:18) is from this root.
Malbim: They do not their acts without time, quickly, and return immediately, like lightning.
What is "k'Mar'e ha'Bazak"?
Rashi: It is sparks. It has the color of fire, e.g. that comes from earthenware used to purify gold in the cauldron. It has colors. Malbim - it is seen for a moment, and then it is gone. He was shown that their mission now is to destroy and burn, but it will not last. The fire will be seen for a moment, and return, for Hashem desires Chesed. 1
Addition in Rashi, citing Bereishis Rabah 50:1: Bazak is an expression of scattering, like one scatters Gefes (the waste of olives after the oil was extracted) in an oven. It burns quickly and raises a flame, and it descends. We find 'Bozekin (we scatter) salt on the Mizbe'ach, lest Kohanim slip (Eruvin 10:4).
Radak: Bazak is like Barak (lightning). The Targum is Barka. It is "Ratzo va'Shov" - it is seen for a moment; it goes quickly, and then it is not seen.
Malbim: Micha'el goes in one jump, and Gavri'el in two (Brachos 4b) Micha'el is the angel of Chesed - he flies in one jump, and does not return. Gavri'el is the angel of Din. He returns immediately, and does not remain there. He flies in two jumps -there and back. (How will Malbim explain 'Eliyahu requires four, and the Malach ha'Maves eight' (ibid.)? - PF)
