2 Chronicles 31:17

They distributed also to those recorded by genealogy of the priests by their ancestral families and the Levites 20 years old and above, by their responsibilities in their divisions;

1 Chronicles 23:24

These were the sons of Levi by their ancestral houses—the heads of families, according to their registration by name in the headcount—20 years old or more, who worked in the service of the Lord’s temple.

1 Chronicles 23:27

for according to the last words of David, the Levites 20 years old or more were to be counted—

Numbers 3:15

“Register the Levites by their ancestral houses and their clans. You are to register every male one month old or more.”

Numbers 3:20

Merari’s sons by their clans were Mahli and Mushi. These were the Levite clans by their ancestral houses.

Numbers 4:3

men from 30 years old to 50 years old—everyone who is qualified to do work at the tent of meeting.

Numbers 4:38

The Gershonites were registered by their clans and their ancestral houses,

Numbers 4:42

The men of the Merarite clans were registered by their clans and their ancestral houses,

Numbers 4:46

Moses, Aaron, and the leaders of Israel registered all the Levites by their clans and their ancestral houses,

Numbers 8:24

“In regard to the Levites: From 25 years old or more, a man enters the service in the work at the tent of meeting.

Numbers 17:2-3

“Speak to the Israelites and take one staff from them for each ancestral house, 12 staffs from all the leaders of their ancestral houses. Write each man’s name on his staff.

1 Chronicles 24:20-26

As for the rest of Levi’s sons:
from Amram’s sons: Shubael;
from Shubael’s sons: Jehdeiah.

2 Chronicles 31:2

Hezekiah reestablished the divisions of the priests and Levites for the burnt offerings and fellowship offerings, for ministry, for giving thanks, and for praise in the gates of the camp of the Lord, each division corresponding to his service among the priests and Levites.

Ezra 2:59

The following are those who came from Tel-melah, Tel-harsha, Cherub, Addan, and Immer but were unable to prove that their families and ancestry were Israelite:

Treasury of Scripture Knowledge

Summary

Both to the genealogy of the priests by the house of their fathers, and the Levites from twenty years old and upward, in their charges by their courses;

Bible References

Genealogy

Numbers 3:15
“Register the Levites by their ancestral houses and their clans. You are to register every male one month old or more.”
Numbers 4:38
The Gershonites were registered by their clans and their ancestral houses,
Numbers 17:2
“Speak to the Israelites and take one staff from them for each ancestral house, 12 staffs from all the leaders of their ancestral houses. Write each man’s name on his staff.
Ezra 2:59
The following are those who came from Tel-melah, Tel-harsha, Cherub, Addan, and Immer but were unable to prove that their families and ancestry were Israelite:

Twenty

Numbers 4:3
men from 30 years old to 50 years old—everyone who is qualified to do work at the tent of meeting.
Numbers 8:24
“In regard to the Levites: From 25 years old or more, a man enters the service in the work at the tent of meeting.
1 Chronicles 23:24
These were the sons of Levi by their ancestral houses—the heads of families, according to their registration by name in the headcount—20 years old or more, who worked in the service of the Lord’s temple.

By their courses

2 Chronicles 31:2
Hezekiah reestablished the divisions of the priests and Levites for the burnt offerings and fellowship offerings, for ministry, for giving thanks, and for praise in the gates of the camp of the Lord, each division corresponding to his service among the priests and Levites.
1 Chronicles 24:20
As for the rest of Levi’s sons:
from Amram’s sons: Shubael;
from Shubael’s sons: Jehdeiah.

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