Just as the garb of the soul affects the way it acts in the body, so too all the different garbs of the various Sefirot and Partzufim affect and change the action of the Line clothed within them in accordance with their particular nature. We find this idea in the statement in the Zohar (Terumah 139a) that bronze is a garment worn by the Indwelling Presence in order to give nourishment to the realm of the husks (קליפות, kelipot).
Similarly, the Tikkuney Zohar (Tikkun #22, 65a) states that “The clothes that He wears in the evening, He does not wear in the morning...”. For the essence is always one and the same, but He clothes Himself in different garbs and executes all His different actions according to the nature of these various garbs. We see this written explicitly: “And He wore righteousness as a coat of mail… and He put on garments of vengeance for clothing “ (Isaiah 59:17).
Thus, when the Supreme Will wanted to bring in the Line to govern the Residue, which is as distant from Him as the body from the soul, an intermediary garment was needed between them, just as the soul needs an intermediary garment in order to connect with the body. It is through this garb that He does what He has to do in the Residue.