Ibn Ezra on Numbers 10:21/אבן עזרא על במדבר י׳:כ״א

1THE BEARERS OF THE SANCTUARY. The reference is to the ark.

2MIGHT BE SET UP. That the Gershonites and the Merarites might set up the tabernacle before the coming of the Kohathites so that the kohanim could immediately bring the ark into its place.