Numbers 3:20 (KJV)

Number the children of Levi after the house of their fathers, by their families: every male from a month old and upward shalt thou number them.

And Moses numbered them according to the word of the LORD, as he was commanded.

And these were the sons of Levi by their names; Gershon, and Kohath, and Merari.

And these are the names of the sons of Gershon by their families; Libni, and Shimei.

And the sons of Kohath by their families; Amram, and Izehar, Hebron, and Uzziel.

Of Gershon was the family of the Libnites, and the family of the Shimites: these are the families of the Gershonites.

Those that were numbered of them, according to the number of all the males, from a month old and upward, even those that were numbered of them were seven thousand and five hundred.

The families of the Gershonites shall pitch behind the tabernacle westward.

And the chief of the house of the father of the Gershonites shall be Eliasaph the son of Lael.

And the charge of the sons of Gershon in the tabernacle of the congregation shall be the tabernacle, and the tent, the covering thereof, and the hanging for the door of the tabernacle of the congregation,