1 Chronicles 24:19

These had their assigned duties for service when they entered the Lord’s temple, according to their regulations, which they received from their ancestor Aaron, as the Lord God of Israel had commanded him.

1 Chronicles 9:25

Their relatives came from their villages at fixed times to be with them seven days,

1 Chronicles 24:1

The divisions of the descendants of Aaron were as follows: Aaron’s sons were Nadab, Abihu, Eleazar, and Ithamar.

2 Chronicles 23:4

This is what you are to do: a third of you, priests and Levites who are coming on duty on the Sabbath, are to be gatekeepers.

2 Chronicles 23:8

So the commanders of hundreds did everything Jehoiada the priest commanded. They each brought their men—those coming on duty on the Sabbath and those going off duty on the Sabbath—for Jehoiada the priest did not release the divisions.

1 Corinthians 14:40

But everything must be done decently and in order.

Hebrews 7:11

If then, perfection came through the Levitical priesthood (for under it the people received the law), what further need was there for another priest to appear, said to be in the order of Melchizedek and not in 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
Their relatives came from their villages at fixed times to be with them seven days,
2 Chronicles 23:4
This is what you are to do: a third of you, priests and Levites who are coming on duty on the Sabbath, are to be gatekeepers.
1 Corinthians 14:40
But everything must be done decently and in order.

Under aaron

1 Chronicles 24:1
The divisions of the descendants of Aaron were as follows: Aaron’s sons were Nadab, Abihu, Eleazar, and Ithamar.
Hebrews 7:11
If then, perfection came through the Levitical priesthood (for under it the people received the law), what further need was there for another priest to appear, said to be in the order of Melchizedek and not in the order of Aaron?

Holman Christian Standard Bible®, Copyright © 1999, 2000, 2002, 2003, 2009 by Holman Bible Publishers.