2 Chronicles 31:17

and those who were reckoned by genealogy of the priests by their fathers' houses, and the Levites from twenty years old and upward, in their offices by their divisions,

1 Chronicles 23:24

These were the sons of Levi after their fathers' houses, even the heads of the fathers of those of them that were counted, in the number of names by their polls, who did the work for the service of the house of LORD, from twenty ye

1 Chronicles 23:27

For by the last words of David the sons of Levi were numbered, from twenty years old and upward.

Numbers 3:15

Number the sons of Levi by their fathers' houses, by their families. Thou shall number them, every male from a month old and upward.

Numbers 3:20

And the sons of Merari by their families: Mahli and Mushi. These are the families of the Levites according to their fathers' houses.

Numbers 4:3

from thirty years old and upward even until fifty years old, all who enter upon the service, to do the work in the tent of meeting.

Numbers 4:38

And those who were numbered of the sons of Gershon, their families, and by their fathers' houses,

Numbers 4:42

And those who were numbered of the families of the sons of Merari, by their families, by their fathers' houses,

Numbers 4:46

All those who were numbered of the Levites, whom Moses and Aaron and the rulers of Israel numbered, by their families, and by their fathers' houses,

Numbers 8:24

This is that which belongs to the Levites: From twenty-five years old and upward they shall go in to wait upon the service in the work of the tent of meeting.

Numbers 17:2-3

Speak to the sons of Israel, and take rods from them, one for each fathers' house, from all their rulers according to their fathers' houses, twelve rods. Write thou every man's name upon his rod.

1 Chronicles 24:20-26

And of 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 after their divisions, every man according to his service, both the priests and the Levites, for burnt-offerings and for peace-offerings, to minister, and to give

Ezra 2:59

And these were those who went up from Tel-melah, Tel-harsha, Cherub, Addan, [and] Immer, but they could not show their fathers' houses, and their seed, 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' houses, by their families. Thou shall number them, every male from a month old and upward.
Numbers 4:38
And those who were numbered of the sons of Gershon, their families, and by their fathers' houses,
Numbers 17:2
Speak to the sons of Israel, and take rods from them, one for each fathers' house, from all their rulers according to their fathers' houses, twelve rods. Write thou every man's name upon his rod.
Ezra 2:59
And these were those who went up from Tel-melah, Tel-harsha, Cherub, Addan, [and] Immer, but they could not show their fathers' houses, and their seed, whether they were of Israel:

Twenty

Numbers 4:3
from thirty years old and upward even until fifty years old, all who enter upon the service, to do the work in the tent of meeting.
Numbers 8:24
This is that which belongs to the Levites: From twenty-five years old and upward they shall go in to wait upon the service in the work of the tent of meeting.
1 Chronicles 23:24
These were the sons of Levi after their fathers' houses, even the heads of the fathers of those of them that were counted, in the number of names by their polls, who did the work for the service of the house of LORD, from twenty ye

By their courses

2 Chronicles 31:2
And Hezekiah appointed the divisions of the priests and the Levites after their divisions, every man according to his service, both the priests and the Levites, for burnt-offerings and for peace-offerings, to minister, and to give
1 Chronicles 24:20
And of the rest of the sons of Levi: Of the sons of Amram, Shubael. Of the sons of Shubael, Jehdeiah.