The following were those who came up from Tel-melah, Tel-harsha, Cherub, Addan, and Immer--they were unable to tell whether their father's house and descent were Israelite: the sons of Delaiah, the sons of Tobiah, the sons of Nekoda--652. Of the sons of the priests, the sons of Habaiah, the sons of Hakkoz, the sons of Barzillai who had married a daughter of Barzillai and had taken his name--these searched for their genealogical records, but they could not be found, so they were disqualified for the priesthood. The Tirshatha ordered them not to eat of the most holy things until a priest with Urim and Thummim should appear. (Ezra 2:59-63; cf. Neh 7:63-64)
Commenting on the above passage, Jacob M. Myers wrote:
[9. Those without proof of ancestry, 59-63]: In the course of the Exile, it was to be expected that certain families lost sight of their ancestry, particularly if they were proselytes, as seems to have been the case with some of them (vs. 59b). More zealous Jews kept their family records intact, while others doubtless devoted much time and effort to search out their genealogies, in view of eventualities such as the one under study (see references to the Talmud in Bowman, p. 585). Ancestral property or family rights could be attested only through the maintenance of family registers (Neh vii 5) that were kept up to date by the local officials so long as the state remained (I Chron v 17). In addition to state records, there were official family registers (I Chron v 7 f., ix 22) that had to be maintained by the family. The registers were now the only way to prove family identity. The five localities mentioned in vs. 59 are otherwise unknown. Only three lay families were involved. Nothing is said about the fate of those families, though they were hardly excluded from the community of Israel. Since we hear no more about them, they evidently were restored to full rights in one way or another. With the priestly families, matters were different, for failure to establish their identity meant disqualification for functioning in the capacity of priests and with it the forfeiture of priestly rights. From the community point of view the situation was even more serious because it involved the possibility of ritual contamination. In any event, these families were barred from exercising their priestly prerogatives, though they were not required to withdraw from the community. The decision to set them aside fell upon the governor (in this case Zerubbabel) who decreed that they must refrain from partaking of the consecrated food (Lev ii 3, vii 21-36) until such time as their case could be disposed of properly, that is, by the use of Urim and Thummim, which was committed to Levi (Deut xxxiii 8) but later restricted to the high priest (Exod xxviii 30; Lev viii 8; Num xxvii 21). Urim and Thummim were oracular instruments or ascertaining the will of God (I. Mendelsohn, IDB, IV, pp. 739-40). Rabbinical tradition affirms that Urim and Thummim were not used after the death of the former prophets (Soṭa, 48a) though Josephus (Antiquities III.viii. 9) seems to assume common knowledge of it in this time. (Jacob M. Myers, Ezra Nehemiah [AB 14; New York: Doubleday, 1965], 19-20)