וּבָ֨א אַהֲרֹ֤ן וּבָנָיו֙ בִּנְסֹ֣עַ הַֽמַּחֲנֶ֔ה וְהוֹרִ֕דוּ אֵ֖ת פָּרֹ֣כֶת הַמָּסָ֑ךְ וְכִ֨סּוּ־בָ֔הּ אֵ֖ת אֲרֹ֥ן הָעֵדֻֽת׃
when the camp setteth forward, Aaron shall go in, and his sons, and they shall take down the veil of the screen, and cover the ark of the testimony with it;
Rashi on Numbers
ובא אהרן ובניו וגו׳ AND [WHEN THE CAMP SETTETH FORWARD,] AARON SHALL COME, AND HIS SONS, etc. — They shall put every object into its wrapping that is prescribed for it in this section, so that the sons of Kohath should have nothing to do except to carry them.
Sforno on Numbers
בנסוע המחנה, after the cloud above it had already withdrawn, for prior to that they were forbidden to enter the Tabernacle.
Rashbam on Numbers
אהרן ובניו בנסוע המחנה, the two “flags” who journeyed first, ahead of the parts of the prefabricated Tabernacle which had been dismantled and which was being transported by the Levites.