Numbers 3:20-24

and the sons of Merari by their families: Mahli and Mushi. These are the families of the Levites according to their fathers’ households.

Of Gershon was the family of the Libnites and the family of the Shimeites; these were the families of the Gershonites.

Their numbered men, in the counting of every male from a month old and upward, their numbered men were 7,500.

The families of the Gershonites were to camp behind the tabernacle westward,

and the leader of the fathers’ households of the Gershonites: Eliasaph the son of Lael. Duties of the Levites