Adam Clarke on 1 Chronicles 24:6

And Shemaiah - "Moses the great scribe, who is called Shemaiah, the son of Nethaneel, of the tribe of Levi, wrote them down." - T.

One principal household - for Eleazar - The family of Eleazar was the most illustrious of the sacerdotal families, because Eleazar was the first-born of Aaron, Ithamar's family was the second in order and dignity; therefore one of the principal families of Eleazar was first taken, and then one of Ithamar's, and thus alternately till the whole was finished.