Numbers

But the Levites shall pitch round about the tabernacle of testimony, that there be no wrath upon the congregation of the children of Israel: and the Levites shall keep the charge of the tabernacle of testimony.

From thirty years old and upward even until fifty years old, all that enter into the host, to do the work in the tabernacle of the congregation.

Then David said, None ought to carry the ark of God but the Levites: for them hath the Lord chosen to carry the ark of God, and to minister unto him for ever.

Yet they shall be ministers in my sanctuary, having charge at the gates of the house, and ministering to the house: they shall slay the burnt offering and the sacrifice for the people, and they shall stand before them to minister unto them.

And that they should keep the charge of the tabernacle of the congregation, and the charge of the holy place, and the charge of the sons of Aaron their brethren, in the service of the house of the Lord.