Matthew Poole and continuators on Ezra 2:62

62 These sought their register among those that were reckoned by genealogy , but they were not found: therefore were they as polluted, put from the priesthood.

The Jews were generally very exact and careful in their Genealogies, partly from their own choice and Interest, that they might preserve the distinctions of the several Tribes and Families, which was necessary both to make out their claims or titles to Offices or inheritances, which might belong to them by death, or otherwise, as here we see, and to govern themselves thereby in the matter of Marriages, and some other things wherein the practice of some Laws required the knowledge of these things: and partly by the special Providence of God, that so it might be certainly known of what Tribe and Family the Messiah was born. For as they took care of all their Families, so doubtless they took a more punctual and singular care about the Royal Family, upon which all their hopes depended.

Marginal references: Heb. they were polluted from the priesthood.