2 Chronicles 31:17

They were to distribute offerings to the priests who were enrolled by families and to the Levites who were at least twenty years old. Distribution was based on the way they served in their divisions.

1 Chronicles 23:24

These were the descendants of Levi by their families, the heads of families as they were registered under their names and counted individually, that is, the workers twenty years old or more who served in the Temple of Jehovah.

1 Chronicles 23:27

According to the last instructions of David, the Levites were counted from those twenty years old or more.

Numbers 3:15

Count the Levites by households and families. Count every male who is at least one month old.

Numbers 3:20

Mahli and Mushi were the sons of Merari. Their families were named after them. These were the households of Levite families.

Numbers 4:3

Register all the men between the ages of thirty and fifty who are qualified to work at the tent of meeting.

Numbers 4:38

The Gershonites were registered by families and households.

Numbers 4:42

The Merarites were registered by families and households.

Numbers 4:46

All the numbered men of the Levites, whom Moses and Aaron and the leaders of Israel counted, by their families and by their fathers' households,

Numbers 8:24

From the age of twenty-five each Levite shall perform his duties in the tent of my presence,

Numbers 17:2-3

Speak to the Israelites and get twelve staffs from them. Get one from the leader of each of their tribes. Write each man's name on his staff.

1 Chronicles 24:20-26

The following men were leaders for Levi's descendants from Kohath: Jehdeiah for Amram's descendants through Shubael,

2 Chronicles 31:2

Hezekiah assigned the priests and the Levites to divisions. Each priest or Levite was put in a division based on the service he performed. The services included: sacrificing burnt offerings, sacrificing fellowship offerings, serving, giving thanks, or praising within the gates of Jehovah's camp.

Ezra 2:59

And these were the people who went up from Telmelah, Telharsha, Cherub, Addan, and Immer. But having no knowledge of their fathers' families or offspring, it was not certain that they were Israelites.

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
Count the Levites by households and families. Count every male who is at least one month old.
Numbers 4:38
The Gershonites were registered by families and households.
Numbers 17:2
Speak to the Israelites and get twelve staffs from them. Get one from the leader of each of their tribes. Write each man's name on his staff.
Ezra 2:59
And these were the people who went up from Telmelah, Telharsha, Cherub, Addan, and Immer. But having no knowledge of their fathers' families or offspring, it was not certain that they were Israelites.

Twenty

Numbers 4:3
Register all the men between the ages of thirty and fifty who are qualified to work at the tent of meeting.
Numbers 8:24
From the age of twenty-five each Levite shall perform his duties in the tent of my presence,
1 Chronicles 23:24
These were the descendants of Levi by their families, the heads of families as they were registered under their names and counted individually, that is, the workers twenty years old or more who served in the Temple of Jehovah.

By their courses

2 Chronicles 31:2
Hezekiah assigned the priests and the Levites to divisions. Each priest or Levite was put in a division based on the service he performed. The services included: sacrificing burnt offerings, sacrificing fellowship offerings, serving, giving thanks, or praising within the gates of Jehovah's camp.
1 Chronicles 24:20
The following men were leaders for Levi's descendants from Kohath: Jehdeiah for Amram's descendants through Shubael,