Numbers 3:21-26

"Of Gershon was the family of the Libnites, and the family of the Shimeites: 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 encamp behind the tabernacle westward. And the prince of the fathers' house of the Gershonites shall be Eliasaph the son of Lael. And the charge of the sons of Gershon in the tent of meeting shall be the tabernacle, and the Tent, the covering thereof, and the screen for the door of the tent of meeting, and the hangings of the court, and the screen for the door of the court, which is by the tabernacle, and by the altar round about, and the cords of it for all the service thereof."

The writing here follows absolutely the style of the 1500 B.C. period with an elaborate, stylized repetition. Also, there is discernible the same Biblical method observed throughout the Pentateuch of including additional and variations of instructions in each repetition. It is foolish indeed to find different "sources" for such supplemental information. It is simply the Biblical method. It will be remembered that God's "two of each kind" orders for Noah's loading the ark were supplemented later with "seven" of the clean kinds of creatures. The result of this is that the total instructions in each sector of labor would be known only by a careful attention to all that was written concerning it, and not by a mere glance at the first mention of it. Most of the critical scholars seem to be unaware of this, losing themselves in a maze of "various sources." In regard to what is said here of the work of the Gershonites, "Their work concerned not the making of these things but their continuance in connection with the movement of the testimony."[13] On the march, the Gershonites followed the company of Reuben (Numbers 10:17).