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 according to their fathers' houses, after their families; every male from a month old and upward shalt thou number them.
Numbers 4:38
And those that were numbered of the sons of Gershon, after their families, and according to their fathers' houses,
Numbers 17:2
Speak unto the children of Israel, and take of them a staff, a staff for each father's house, of all their princes according to the houses of their fathers, twelve staves: thou shalt write each one's name upon his staff.
Ezra 2:59
And these are they that went up from Tel-melah, Tel-harsha, Cherub-Addan, Immer; but they could not shew their fathers' house, nor their seed, whether they were of Israel.

Twenty

Numbers 4:3
from thirty years old and upward even unto fifty years old, all that enter into the service, to do the work in the tent of meeting.
Numbers 8:24
This is that which concerneth the Levites: from twenty-five years old and upward shall he come to labour in the work of the service of the tent of meeting.
1 Chronicles 23:24
These were the sons of Levi according to their fathers' houses, the chief fathers, as they were reckoned, by number of names by their polls, who did the work of the service of the house of Jehovah, from twenty years old and upward.

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, as well the priests as the Levites, for burnt-offerings and for peace-offerings, to serve and to give thanks and to praise in the gates of the courts of Jehovah.
1 Chronicles 24:20
And as for the rest of the sons of Levi: of the sons of Amram, Shubael; of the sons of Shubael, Jehdeiah.