Ezra 2:62
These sought their place among those who were registered by genealogy, but they were not found: therefore were they deemed polluted and put from the priesthood.
Numbers 3:10
And you shall appoint Aaron and his sons, and they shall attend to their priesthood. The stranger who comes near shall be put to death."
Leviticus 21:21-23
no man of the seed of Aaron the priest, who has a blemish, shall come near to offer the offerings of the LORD made by fire. Since has a blemish, he shall not come near to offer the bread of his God.
Numbers 16:39-40
Eleazar the priest took the bronze censers, which those who were burnt had offered; and they beat them out for a covering of the altar,
Numbers 18:7
You and your sons with you shall keep your priesthood for everything concerning the altar, and for that inside the veil; and you shall serve: I give you the priesthood as a service of gift: and the stranger who comes near shall be put to death."
Ezekiel 44:10-14
But the Levites who went far from me, when Israel went astray, who went astray from me after their idols, they shall bear their iniquity.