Numbers 3:10

“You shall gird them with sashes, Aaron and his sons, and bind caps on them, and they shall have the priesthood by a perpetual statute. So you shall ordain Aaron and his sons.

‘No layman, however, is to eat the holy gift; a foreign resident with the priest or a hired man shall not eat of the holy gift.

“So when the tabernacle is to set out, the Levites shall take it down; and when the tabernacle encamps, the Levites shall set it up. But the layman who comes near shall be put to death.

and that He has brought you near, Korah, and all your brothers, sons of Levi, with you? And are you seeking for the priesthood also?

“But bring near with you also your brothers, the tribe of Levi, the tribe of your father, that they may be joined with you and minister to you, while you and your sons with you are before the tent of the testimony.

And the man Micah had a shrine, and he made an ephod and household idols and ordained one of his sons, and he became his priest.

And they stood against Uzziah the king and said to him, “It is not for you, Uzziah, to burn incense to Yahweh, but for the priests, the sons of Aaron who are set apart as holy to burn incense. Get out of the sanctuary, for you have been unfaithful and will have no honor from Yahweh God.”

and the Levitical priests shall not have a man cut off from before Me who is to offer burnt offerings, to offer up grain offerings in smoke, and to perform sacrifices continually.’”

“Yet they shall be ministers in My sanctuary, having oversight at the gates of the house and ministering in the house; they shall slaughter the burnt offering and the sacrifice for the people, and they shall stand before them to minister to them.