In Numbers 9:3, this signifies the representation of holy things. (Arcana Coelestia 4581[2, 3])

177. THE GARMENTS WITH WHICH ANGELS ARE SEEN TO BE CLOTHED

Because angels are men, and live together as men do on earth, therefore, they have garments, dwellings and other such things, with the difference, however, that as they are in a more perfect state, all the things they have are in greater perfection. For, as angelic wisdom surpasses human wisdom to such a degree as to be described as ineffable, so it is also with all things that are perceived and seen by angels, inasmuch as all things perceived and seen by them correspond to their wisdom (see above 173).