Ezra 2:62
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. 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.
Ezra 2:62 belongs to the account of those who answered the decree of Cyrus and returned to Jerusalem to their own land, nearly fifty thousand Jews made free to go, when the temple was begun, and it helps identify that returned group and the care taken over lineage. A priest had to prove his direct descent from Aaron in the genealogical records. Some who claimed priestly descent and a place in priestly service searched for their names in the official genealogical register but were not found, and therefore were treated as ceremonially unclean or polluted and excluded from the priesthood and its service. The same exclusion is recorded for those who claimed priestly descent but could not find their names entered, who were put from the priesthood as ceremonially unclean.
Their lineage might have qualified them, but accepting them without proof risked allowing unauthorized priests to serve and contaminating the sanctuary service, so the question of their eligibility was left for a priest to determine by Urim and Thummim. To be described in this connection as without ancestry means that lineage was missing from the records, not that the persons had no ancestors.
Their exclusion illustrates that the priesthood had become corrupted by the time the people returned from Babylonian captivity. The requirement serves as a type of the need for Christians to be directly connected with Christ, the heavenly High Priest, to belong to the royal priesthood. By contrast, Christ's priesthood and the kingship united with it in the pattern of Melchizedek does not depend on genealogy, and his place on God's throne is for his priestly work, not inherited descent, yet when he takes David's throne he does so as the Son of David, whose genealogy must be traced. The passage gives no further explanation of the genealogical disqualification from the priesthood.