These are the clans of Levi: the clan of the Libnites, the clan of the Hebronites, the clan of the Mahlites, the clan of the Mushites, the clan of the Korahites. And Kohath was the father of Amram.
Levi was God's tribe, a tribe that was to have no inheritance with the rest in the land of Canaan, and therefore was not numbered with the rest, but by itself; so it had been numbered in the beginning of this book at Mount Sinai, and therefore came not under the sentence passed upon all that were then numbered, that none of them should enter...
Commenting on Numbers 26:57-62
families of the Levites--The census of this tribe was taken separately, and on a different principle from the rest. (See Exo 6:16-19).
Num 26:57-59 Mustering of the Levites. - The enumeration of the different Levitical families into which the three leading families of Levi, that were founded by his three sons Gershon, Kohath, and Merari, were divided, is not complete, but is broken off in Num 26:58 after the notice of five different families, for the purpose of tracing once more the descent of Moses and Aaron...
Commenting on Numbers 26:57-59