Numbers 10:21

And the other did set up the tabernacle— The other is not in the text: Calmet explains it, "that the Kohathites set up the tabernacle against they, i.e. the priests, arrived." Houbigant renders it, and the Kohathites set forward, bearing the sacred things, and the tabernacle was erected while they came. The two families, says he, of the Levites, Gershon and Merari, march after the tribe of Judah; that, the front of the army standing still, and pitching their tents, they might erect, without any delay, the tabernacle, when it was to be erected: that so the Kohathites might find it prepared to receive the holy vessels, when they came after the second part of the army: and this is taken notice of in the first march of the Israelites, as it was to be the rule of all the rest.