Ezra 2:62
They searched for their records in the genealogical materials, but did not find them. They were therefore excluded from the priesthood.
Numbers 3:10
So you are to appoint Aaron and his sons, and they will be responsible for their priesthood; but the unauthorized person who comes near must be put to death."
Leviticus 21:21-23
No man from the descendants of Aaron the priest who has a physical flaw may step forward to present the Lord's gifts; he has a physical flaw, so he must not step forward to present the food of his God.
Numbers 16:39-40
So Eleazar the priest took the bronze censers presented by those who had been burned up, and they were hammered out as a covering for the altar.
Numbers 18:7
But you and your sons with you are responsible for your priestly duties, for everything at the altar and within the curtain. And you must serve. I give you the priesthood as a gift for service; but the unauthorized person who approaches must be put to death."
Ezekiel 44:10-14
"'But the Levites who went far from me, straying off from me after their idols when Israel went astray, will be responsible for their sin.