Numbers 3-4

Numbers 3
Aaron has four sons. The Lord killed the two oldest because they offered profane fire to the Lord.
The Levites are to serve Aaron and his sons in their priestly duties in the Tabernacle.
All the first borns, man or beast, are the Lord's.
The Levites are to be counted numbering every male from a month old and above.
The Levites were numbered at 22,000.
The Lord declares the Levites His instead of taking the firstborns of every tribe.

Numbers 4
The duties of the sons of Kohath are to cover the holy things.
The duties of the sons of Gershon are to carry the curtains, the screen door, and hangings of the court.
The duties of the sons of Merari are to carry the boards, bars, pillars and sockets.
Those of the Levites from 30 to 50 years old were 8,580.