Albert Barnes Commentary Numbers 10:17

"And the tabernacle was taken down; and the sons of Gershon and the sons of Merari, who bare the tabernacle, set forward." — Numbers 10:17 (ASV)

A more precise determination of the method for carrying out the order given in (Numbers 2:17). The appointed place of the tabernacle, in the midst of the host, was represented during the march by the ark, the holy vessels, and other items carried by the Kohathites. The actual structure of the tabernacle was carried ahead by the Gershonites and Merarites, immediately behind the camp of Judah, so that it could be set up and ready for the arrival of the sacred utensils carried by the Kohathites. Compare (Numbers 2) and (Numbers 4).