These sought their registration among those enrolled in the genealogies, but they were not found there, and so they were excluded from the priesthood as unclean.
Here is an account, I. Of the priests that returned, and they were a considerable number, about a tenth part of the whole company: for the whole were above 42,000 (Ezr 2:64), and four families of priests made up above 4200 (Ezr 2:36-39); thus was the tenth God's part - a blessed decimation.
Commenting on Ezra 2:36-63
Besides their servants and their maids, of whom there were seven thousand three hundred thirty and seven,.... This shows that the greater part of those that returned were of the poorer sort, since there were so few servants that belonged unto them; these came not into the above account: and there were among them two hundred singing men and singing women; among the servants, who...
Ezr 2:61-62 Priests who could not prove themselves members of the priesthood. Comp. Neh 7:63-65. - Three such families are named: the sons of Habaiah, the sons of Hakkoz, the sons of Barzillai. These could not discover their family registers, and were excluded from the exercise of priestly functions.
Commenting on Ezra 2:61-62