2 Chronicles 31:17

as well as the priests who were registered genealogically according to their fathers’ households, and the Levites from twenty years old and upward, by their duties and by their divisions.

1 Chronicles 23:24

These were the Levites by their fathers’ households, the heads of the fathers’ households of those registered, according to the number of names of the individuals who were the servants of the house of the Lord, from twenty years old and upward.

1 Chronicles 23:27

For by the last words of David, the Levites from twenty years old and above were counted.

Numbers 3:15

“Number the sons of Levi by their fathers’ households, by their families (clans). You shall number every male from a month old and upward.”

Numbers 3:20

and the [two] sons of Merari by their families: Mahli and Mushi. These are the families of the Levites by their fathers’ households.

Numbers 4:3

from thirty years old and upward, even to fifty years old, all who enter the service to do the work in the Tent of Meeting (tabernacle).

Numbers 4:38

The men who were numbered of the sons of Gershon, by their families (clans), and by their fathers’ households,

Numbers 4:42

The men who were numbered of the sons of Merari, by their families (clans), by their fathers’ households,

Numbers 4:46

All the men who were numbered of the Levites, whom Moses and Aaron and the leaders of Israel counted by their families (clans) and by their fathers’ households,

Numbers 8:24

“This is what applies to the Levites: from twenty-five years old and upward they shall enter to perform service in the work of the Tent of Meeting,

Numbers 17:2-3

“Speak to the sons of Israel and get rods from them, a rod for each father’s household, from all their leaders according to their fathers’ households, twelve rods. Write every man’s name on his rod,

1 Chronicles 24:20-26

Now as for the rest of the sons of Levi: of the sons of Amram: Shubael; of the sons of Shubael: Jehdeiah.

2 Chronicles 31:2

And Hezekiah appointed the divisions of the priests, and the Levites by their divisions, each in accordance with his service, both the priests and Levites, for burnt offerings and for peace offerings, to minister and to give thanks and to praise in the gates of the camp of the Lord.

Ezra 2:59

Now these are the ones who came up from Tel-melah, Tel-harsha, Cherub, Addan, and Immer, but they could not provide evidence of their fathers’ households and their descendants, whether they were of Israel:

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
“Number the sons of Levi by their fathers’ households, by their families (clans). You shall number every male from a month old and upward.”
Numbers 4:38
The men who were numbered of the sons of Gershon, by their families (clans), and by their fathers’ households,
Numbers 17:2
“Speak to the sons of Israel and get rods from them, a rod for each father’s household, from all their leaders according to their fathers’ households, twelve rods. Write every man’s name on his rod,
Ezra 2:59
Now these are the ones who came up from Tel-melah, Tel-harsha, Cherub, Addan, and Immer, but they could not provide evidence of their fathers’ households and their descendants, whether they were of Israel:

Twenty

Numbers 4:3
from thirty years old and upward, even to fifty years old, all who enter the service to do the work in the Tent of Meeting (tabernacle).
Numbers 8:24
“This is what applies to the Levites: from twenty-five years old and upward they shall enter to perform service in the work of the Tent of Meeting,
1 Chronicles 23:24
These were the Levites by their fathers’ households, the heads of the fathers’ households of those registered, according to the number of names of the individuals who were the servants of the house of the Lord, from twenty years old and upward.

By their courses

2 Chronicles 31:2
And Hezekiah appointed the divisions of the priests, and the Levites by their divisions, each in accordance with his service, both the priests and Levites, for burnt offerings and for peace offerings, to minister and to give thanks and to praise in the gates of the camp of the Lord.
1 Chronicles 24:20
Now as for the rest of the sons of Levi: of the sons of Amram: Shubael; of the sons of Shubael: Jehdeiah.