1 Samuel 2:11
Then Elkanah went home to Ramah, but the boy began ministering to the LORD before Eli the priest.

2 Chronicles 8:14
In keeping with the ordinances of his father David, Solomon appointed the divisions of the priests over their service, and the Levites for their duties to offer praise and to minister before the priests according to the daily requirement. He also appointed gatekeepers by their divisions at each gate, for this had been the command of David, the man of God.

2 Chronicles 31:2
Hezekiah reestablished the divisions of the priests and Levites—each of them according to their duties as priests or Levites—for the burnt offerings and peace offerings, for ministry, for giving thanks, and for singing praises at the gates of the LORD’s dwelling.

Nehemiah 12:44-47
And on that same day men were appointed over the rooms that housed the supplies, contributions, firstfruits, and tithes. The portions specified by the Law for the priests and Levites were gathered into these storerooms from the fields of the villages, because Judah rejoiced over the priests and Levites who were serving. / They performed the service of their God and the service of purification, along with the singers and gatekeepers, as David and his son Solomon had prescribed. / For long ago, in the days of David and Asaph, there were directors for the singers and for the songs of praise and thanksgiving to God. ...

1 Chronicles 23:28-32
but their duty was to assist the descendants of Aaron with the service of the house of the LORD, being responsible for the courts and chambers, the purification of all the holy things, and the work of the service of the house of God, / as well as for the rows of the showbread, the fine flour for the grain offering, the wafers of unleavened bread, the baking, the mixing, and all measurements of quantity and size. / They were also to stand every morning to give thanks and praise to the LORD, and likewise in the evening. ...

2 Kings 11:5-9
and commanded them, “This is what you are to do: A third of you who come on duty on the Sabbath shall guard the royal palace, / a third shall be at the gate of Sur, and a third at the gate behind the guards. You are to take turns guarding the temple— / the two divisions that would go off duty on the Sabbath are to guard the house of the LORD for the king. ...

1 Chronicles 9:25
Their relatives came from their villages at fixed times to serve with them for seven-day periods.

1 Chronicles 24:19
This was their appointed order for service when they entered the house of the LORD, according to the regulations prescribed for them by their forefather Aaron, as the LORD, the God of Israel, had commanded him.

2 Chronicles 5:11
Now all the priests who were present had consecrated themselves regardless of their divisions. And when the priests came out of the Holy Place,

2 Chronicles 29:11
Now, my sons, do not be negligent, for the LORD has chosen you to stand before Him, to serve Him, to minister before Him, and to burn incense.”

Exodus 29:30
The son who succeeds him as priest and enters the Tent of Meeting to minister in the Holy Place must wear them for seven days.

Leviticus 8:33-35
You must not go outside the entrance to the Tent of Meeting for seven days, until the days of your ordination are complete; for it will take seven days to ordain you. / What has been done today has been commanded by the LORD in order to make atonement on your behalf. / You must remain at the entrance to the Tent of Meeting day and night for seven days and keep the LORD’s charge so that you will not die, for this is what I have been commanded.”

Numbers 8:24-26
“This applies to the Levites: Men twenty-five years of age or older shall enter to perform the service in the work at the Tent of Meeting. / But at the age of fifty, they must retire from performing the work and no longer serve. / After that, they may assist their brothers in fulfilling their duties at the Tent of Meeting, but they themselves are not to do the work. This is how you are to assign responsibilities to the Levites.”

Numbers 18:5-7
And you shall attend to the duties of the sanctuary and of the altar, so that wrath may not fall on the Israelites again. / Behold, I Myself have selected your fellow Levites from the Israelites as a gift to you, dedicated to the LORD to perform the service for the Tent of Meeting. / 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.”

Hebrews 9:6
When everything had been prepared in this way, the priests entered regularly into the first room to perform their sacred duties.