Bede

And from the sons of the priests, the sons of Tobiah, etc. The sons of the exiled act with the same caution towards the priests as they are reported to have acted towards the people. For they took great care that it would be openly revealed without confusion who truly belonged to the people of Israel or to the priestly lineage; but those who were suspected, or who were certainly begotten from the lineage of proselytes, that is, foreigners. …

Commentary on Ezra and Nehemiah ↗