What is the meaning of "u'Fekudav asher Tzivah Hashem Es Moshe"?
Ramban #2 (citing Ibn Ezra): This refers to all the members of Gershon, Kehas and Merari
See Ramban, who has a different text in Rashi.
Ramban: As if it had written "Ka'asher" (with a 'Kaf').
As the Ramban explained in Bamidbar. Refer to 4:32:3:1**. No ben Levi was permitted to perform a Melachah to which he was not designated. In fact the Sifri relates an episode where R. Yehoshua ben Chananyah, who was a singer, went to assist R. Yochanan ben Gudgodah to shut the gates, and the latter stopped him, because a singer who opens or shuts the gates is Chayav Misah (bi'Yedei Shamayim).
Seforno: As the Torah indicated earlier in Pasuk 32.