Numbers 3:7

“At the doorway of the tent of meeting, moreover, you shall remain day and night for seven days and keep the charge of Yahweh, so that you will not die, for so I have been commanded.”

“But you shall appoint the Levites over the tabernacle of the testimony and over all its furnishings and over all that belongs to it. They shall carry the tabernacle and all its furnishings, and they shall attend to it; they shall also camp around the tabernacle.

“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 from the sons of Israel’s half, you shall take one drawn out of every fifty of the persons, of the cattle, of the donkeys, and of the sheep, from all the animals, and give them to the Levites who keep charge of the tabernacle of Yahweh.”

Thus they shall keep responsibility of the tent of meeting, and responsibility of the holy place, and responsibility of the sons of Aaron their relatives, for the service of the house of Yahweh.

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.