Numbers 3:10

And you shall appoint Aaron and his sons , and they shall guard their priesthood . But if any outsider comes near, he shall be put to death .

Appoint Aaron and his sons to serve as priests; anyone else who approaches the sanctuary is to be put to death.”

And thou shalt appoint Aaron and his sons, and they shall wait on their priest's office : and the stranger that cometh nigh shall be put to death.