1 Chronicles 24:19

These [were] their appointments for their service to come into the house of Yahweh according to their custom by the hand of Aaron their father, as Yahweh the God of Israel had commanded him.

1 Chronicles 9:25

And their brethren in their villages [were] to come [every] seven days {by turn} [to be] with these.

1 Chronicles 24:1

And as for the sons of Aaron, [these were] their divisions. The sons of Aaron [were] Nadab and Abihu, Eleazar and Ithamar.

2 Chronicles 23:4

This is the thing that you must do: one third of you priests and Levites {coming off duty on the Sabbath} [shall be] gatekeepers at the entrances

2 Chronicles 23:8

And the Levites and all Judah did according to all that Jehoiada the priest commanded. And they each took his men [who were] {coming off duty on the Sabbath} with {the ones going out to duty on the Sabbath}, for Jehoiada the priest did not dismiss the working groups.

1 Corinthians 14:40

But let all [things] be [done] decently and according to proper procedure.

Hebrews 7:11

Thus if perfection was through the Levitical priesthood, for on the basis of it the people received the law, what further need [is there] for another priest to arise according to the order of Melchizedek and not said to be according to the order of Aaron?

Treasury of Scripture Knowledge

Summary

These were the orderings of them in their service to come into the house of the LORD, according to their manner, under Aaron their father, as the LORD God of Israel had commanded him.

Bible References

The orderings

1 Chronicles 9:25
And their brethren in their villages [were] to come [every] seven days {by turn} [to be] with these.
2 Chronicles 23:4
This is the thing that you must do: one third of you priests and Levites {coming off duty on the Sabbath} [shall be] gatekeepers at the entrances
1 Corinthians 14:40
But let all [things] be [done] decently and according to proper procedure.

Under aaron

1 Chronicles 24:1
And as for the sons of Aaron, [these were] their divisions. The sons of Aaron [were] Nadab and Abihu, Eleazar and Ithamar.
Hebrews 7:11
Thus if perfection was through the Levitical priesthood, for on the basis of it the people received the law, what further need [is there] for another priest to arise according to the order of Melchizedek and not said to be according to the order of Aaron?