This first phase of a two-part registration of the tribe of Levi summarized each family's special duties. 4:1–33 describes this in more detail (see 4:34–49 for the second phase). This count did not relate to military duties, so it included male Levites from the age of one month (3:40–41).
Three family groups descend from the three sons of Levi: Gershon, Kohath, and Merari. These clans, often called the Gershonites, Kohathites, and Merarites, later inherited the "cities of refuge" (Joshua 21). They also had various important roles in the Jerusalem temple (2 Chronicles 29:3–17).