Moses did not arrange the three Levitical families in the text here in the order of the ages of their founders. He arranged them in the order of the holiness of the articles that they managed.
The Kohathites--who included Moses, Aaron, and the priests--were in charge of the tabernacle furniture including the ark. God told them how to prepare the various pieces of furniture for travel and how to carry them. The priests wrapped the articles of furniture, except the laver, and then the other Kohathites carried them. Touching a holy piece of furniture or even looking at one would result in death (vv. 15, 20). The oils, incense, and the flour for the daily meal offering were the special responsibility of Eleazer, the heir to the high priest's office (v. 16).
God also explained the responsibilities of the Gershonites (vv. 21-28) and the Merarites (vv. 29-33).
There were 8,580 Levites who were fit for service (v. 48). A Levite had to be at least 30 and not more than 50 years old to participate in these acts of ministry (cf. 8:23-26).
"The truth is that all work in the kingdom of God is royal service, however unostentatious and, from the human standpoint, lowly and insignificant."32
"The sense of order and organization already observed in this book comes to its finest point in this chapter. Again, we observe that the standard pattern in Hebrew prose is a movement from the general to the specific, from the broad to the particular. Chapters 1-4 follow this concept nicely. . . . The chapters have moved from the nation as a whole to the particular families of the one tribe that has responsibility to maintain the symbols of Israel's worship of the Lord. Each chapter gets more specific, more narrow in focus, with the central emphasis on the worship of the Lord at the Tent of Meeting."33
An emphasis in this book appears at the end of this chapter again (v. 51). Moses carried out the Lord's commands exactly (cf. 1:54; 3:33-34; 4:42; Heb. 3:5).
