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. Under Aaron their father - That is, they followed the order and plans laid down by Aaron during his lifetime.
Related Commentaries of 1 Chronicles 24:19
1 Chronicles 24:19
19 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.