What are the connotations of the word "Mishmeres"?
Rashi: It means 'a charge' - any appointment that one is designated to fulfill. 1
Targum Yonasan: "Veshamru es Mishmarto" actually refers to the ultimate division of the Kohanim into twenty-four groups who were destined to serve in rotation in the Beis-ha'Mikdash.
What are the connotations of " ... ve'es Mishmares Kol ha'Eidah"?
Oznayim la'Torah: It means that the Levi'im serve, not only Aharon (and the Kohanim) with their singing, but also Yisrael, in their capacity as their Sheluchim (emissaries). 1
See Oznayim la'Torah. This is difficultt however, since that is inherent in the continuation of the Pasuk "ve'es Mishmeres B'nei Yisrael"?
To whom is "Mishmares Kol ha'Eidah" referring?
Seforno It is referring to the Sanhedrin, who, If not for the Eigel, would have been responsible for matters concerning the Avodah. The Levi'im were now being designated to replace them.
Refer to 3:7:1.1:1.