Priests: All Except Seed of Aaron Excluded from Being
Source: TTT
Numbers 3:10
So you shall appoint Aaron and his sons to carry out the duties of the priesthood; but any outsider who approaches the tabernacle must be put to death.”
Numbers 16:40
just as the LORD commanded him through Moses. This was to be a reminder to the Israelites that no outsider who is not a descendant of Aaron should approach to offer incense before the LORD, lest he become like Korah and his followers.
Numbers 18:7
But only you and your sons shall attend to your priesthood for everything concerning the altar and what is inside the veil, and you are to perform that service. I am giving you the work of the priesthood as a gift, but any outsider who comes near the sanctuary must be put to death.”