New Revised Standard Version
These had as their appointed duty in their service to enter the house of the LORD according to the procedure established for them by their ancestor Aaron, as the LORD God of Israel had commanded him.

Contemporary English Version
These men were assigned their duties at the temple, just as the LORD God of Israel had commanded their ancestor Aaron.

New American Bible
This was the appointed order of their service when they functioned in the house of the LORD according to the precepts given them by Aaron, their father, as the LORD, the God of Israel, had commanded him.

Douay-Rheims Bible
These are their courses according to their ministries, to come into the house of the Lord, and according to their manner under the hand of Aaron their father: as the Lord the God of Israel had commanded.

These are their courses according to their ministries, to come into the house of the Lord, and according to their manner under the hand of Aaron their father: as the Lord the God of Israel had commanded.

the orderings

1 Chronicles 9:25 And their brethren dwelt in village, and came upon their sabbath days from time to time.

2 Chronicles 23:4,5,8 And this is the thing that you shall do: . . .

1 Corinthians 14:40 But let all things be done decently and according to order.

under Aaron

1 Chronicles 24:1 Now these were the divisions of the sons of Aaron: The sons of Aaron: Nadab, and Abiu, and Eleazar, and Ithamar.

Hebrews 7:11 If then perfection was by the Levitical priesthood (for under it the people received the law), what further need was there that another priest should rise according to the order of Melchisedech: and not be called according to the order of Aaron?