And to whom does "u'Shemartem es Mishmeres ha'Kodesh ... " refer?
Seforno: It refers to the Kohanim, who are obligated to guard the Mishkan within the walls. 1
It is not clear however, how the Kohanim can possibly guard the Mizbe'ach ha'Olah from within the Kodesh?
Why does the Torah add the word "Od"?
Rashi: It means that there will not be anger again, like there was above (in 17:11).