The Torah, “Exodus (Tetzaveh),” 29:29-29:30: The holy garments that are Aaron’s shall be for his sons after him, to be exalted through them and invested with full authority through them. Seven days shall the one son of his sons [who will be] the Kohen in his place wear them, the one who is to enter the Tent of Meeting to serve in the holy.
The spiritual levels constantly rise since they are constantly corrected adding new levels to the ladder, which are the soul. In order to rise to the level Aaron was on previously, it takes seven days, which symbolizes the seven lower Sefirot, to correct the attributes of HGT NHYM.
It’s like a regulator, and because a person who ascends to this level has to be corrected this way in order to become totally similar to these garments, to the corrections of Aaron that were made on this level, then it’s as if a person enters Aaron’s role, Aaron’s level.
From KabTV’s “Secrets of the Eternal Book” 8/28/13