Tabernacle: The Priests: Performed all Services In
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 18:1, 2
So the LORD said to Aaron, “You and your sons and your father’s house must bear the iniquity involving the sanctuary. And you and your sons alone must bear the iniquity involving your priesthood. / But bring with you also your brothers from the tribe of Levi, the tribe of your father, that they may join you and assist you and your sons before the Tent of the Testimony.
Hebrews 9:6
When everything had been prepared in this way, the priests entered regularly into the first room to perform their sacred duties.