Rashi on Numbers 3:21/רש"י על במדבר ג׳:כ״א

1לגרשון משפחת הלבני OF GERSHON, THE FAMILY OF THE LIBNITES — that is to say: Of Gershon, those who were numbered were the family of the Libnites and the family of the Shimites; and the section concludes with the statement (v. 22) “those who were numbered of them were so-and-so many”.