Numbers 3:1

These also are the generations of Aaron and Moses in the day that the LORD spake with Moses in mount Sinai.

The book of Numbers takes its name from the two numberings of Israel, one in the early part of the book and one near its close. This verse stands in the opening part, within the first four chapters, which deal with the numbering of the people, the numbering of the tribe of Levi, and the office of the various families of Levi. It introduces the account of the duties of the Levites around the sanctuary. That tribe was divided by Gershon, Kohath, and Merari, whose families camped on assigned sides of the tabernacle and were given its care and service, while Moses, Aaron, and Aaron's sons camped on the east side and kept the charge of the sanctuary.

The tribe of Levi belonged to God, and the priesthood was vested in that tribe. Priestly service under the Aaronic order belonged to the tribe of Levi from the Exodus until the Crucifixion. The verse belongs to the levitical law given to the children of Israel, which is separate from the law of God, and the law of God is absolute and perpetual, holy, just, and good. The levitical law was appointed only for that age until the type met its antitype, and it was abolished by Christ.