20 And the sons of Merari by their families: Mahli and Mushi. These are the families of the Levites by their fathers' houses. 21 From Gershon came the family of the Libnites and the family of the Shimites; these were the families of the Gershonites. 22 Those who were numbered, according to the number of all the males from a month old and above--of those who were numbered there were seven thousand five hundred. 23 The families of the Gershonites were to camp behind the tabernacle westward. 24 And the leader of the fathers' house of the Gershonites was Eliasaph the son of Lael. 25 The duties of the children of Gershon in the tabernacle of meeting included the tabernacle, the tent with its covering, the screen for the door of the tabernacle of meeting, 26 the screen for the door of the court, the hangings of the court which are around the tabernacle and the altar, and their cords, according to all the work relating to them. 27 From Kohath came the family of the Amramites, the family of the Izharites, the family of the Hebronites, and the family of the Uzzielites; these were the families of the Kohathites. 28 According to the number of all the males, from a month old and above, there were eight thousand six hundred keeping charge of the sanctuary. 29 The families of the children of Kohath were to camp on the south side of the tabernacle. 30 And the leader of the fathers' house of the families of the Kohathites was Elizaphan the son of Uzziel. 31 Their duty included the ark, the table, the lampstand, the altars, the utensils of the sanctuary with which they ministered, the screen, and all the work relating to them. 32 And Eleazar the son of Aaron the priest was to be chief over the leaders of the Levites, with oversight of those who kept charge of the sanctuary. 33 From Merari came the family of the Mahlites and the family of the Mushites; these were the families of Merari. 34 And those who were numbered, according to the number of all the males from a month old and above, were six thousand two hundred. 35 The leader of the fathers' house of the families of Merari was Zuriel the son of Abihail. These were to camp on the north side of the tabernacle.
Matthew Henry's Commentary on Numbers 3:20-35
Commentary on Numbers 3:14-39
(Read Numbers 3:14-39)
The Levites were in three classes, according to the sons of Levi; Gershon, Kohath, and Merari; and these were subdivided into families. The posterity of Moses were not at all honoured or privileged, but stood upon the level with other Levites; thus it was plain, that Moses did not seek the advancement of his own family, or to secure any honours to it. The tribe of Levi was by much the least of all the tribes. God's chosen are but a little flock in comparison with the world.