1)
What do we learn from "Ish k'Fi Avodaso"?
1.
'Rashi': Kohanim serve, and Leviyim sing and guard gates. Everyone does his proper Avodah.
2.
Malbim: Kohanim offer "l'Olah veli'Shlamim"; Leviyim serve, e.g. Shechitah and flaying, and Lehodos u'Lehael - singing.
2)
What are Sha'arei Machanos Hashem?
1.
Malbim: Leviyim lodged in the gates, to guard.
