Which chamber is this?
Radak: It is the chamber mentioned above (44) that faces north.
What is the difference between "Shomerei Mishmeres ha'Mizbe'ach" and "Shomerei Mishmeres ha'Bayis" in the previous verse? And why did they need a separate chamber?
Vilna Gaon, Malbim: The former serve on the Mizbe'ach; the latter do not. (Refer to 40:44:3:2.)
Why does it mention Tzadok?
Radak: He was the first Kohen Gadol in Bayis Rishon - "va'Yamlichu Shenis li'Shlomo ben David va'Yimshechu la'Shem l'Nagid ul'Tzadok ha'Kohen" (Divrei ha'Yamim I, 29:22). He descended from Pinchas ben Elazar; Bris Kehunah was given to his seed. Bnei Itamar were demoted from the attribute of Kehunah via the curse of [Bnei] Eli.
Malbim: His descendants engage in Avodah. Therefore, their chamber was in the south, for the ramp that ascends to the Mizbe'ach was in the south. Their chamber was opposite the 15 Amos to the side of the eastern gate, in the south, where there were no Ulamos. It was close to the Mizbe'ach in Ezras Kohanim, therefore there was room only for one.
Why does it say "ha'Kerevim"?
Vilna Gaon: They offer Korbanos to Hashem, to serve Him.
