Preparing the High Priest for his sacred duties was a precise and deeply significant process. Moses acted as a dedicated deputy, personally preparing his brother Aaron for his new role [אדרת אליהו].
A profound sense of modesty guided this preparation. The trousers are notably absent from the narrative of Moses dressing his brother. Out of respect for modesty, Aaron put the trousers on himself immediately after his purification immersion, rather than having Moses dress him [פרדס יוסף, פירושי רד״צ הופמן, ברכת אשר על התורה]. This careful boundary extended to the tunic as well. Moses merely placed the tunic over Aaron's head, allowing Aaron to pull it down over his own body so that Moses would not touch his covered areas [העמק דבר, ברכת אשר על התורה]. Because Moses took on the intimate and honorable task of dressing his brother, he later earned the right to undress Aaron on the day of his death [מלבי״ם].
The practical sequence of putting on the garments followed a strict logic, differing slightly from the original instructions given earlier. Instead of grouping all the sashes together, Moses dressed Aaron step by step: the tunic, immediately followed by its sash, and then the robe and the ephod [רמב״ן, הטור הארוך, פירושי רד״צ הופמן]. The guiding principle was that it is improper to wear a garment without a belt. Therefore, securing the garments happened instantly—the sash directly after the tunic, and the belt of the ephod right after the ephod was placed, before adding the breastplate [רמב״ן, הטור הארוך].
Moses completed outfitting Aaron entirely before turning his attention to Aaron's sons. The sash used to secure Aaron's tunic was completely identical to those worn by regular priests, with both types made from a specific mixture of linen and wool [תורה תמימה, העמק דבר, אדרת אליהו]. The physical process concluded with the ephod, whose belt was fastened tightly over the rest of the clothing [ביאור שטיינזלץ]. Moses carefully wrapped, tied, and adorned Aaron in this final piece [אבן עזרא, ביאור שטיינזלץ].
Beyond the physical actions, donning these garments carried deep cosmic symbolism. The eight garments of the High Priest correspond directly to the seven heavens and the celestial bodies. For instance, the trousers parallel the lowest heaven, the tunic aligns with the heaven of the stars, the robe corresponds to the heaven of the sun, and the golden plate on his head represents the Throne of Glory. Through these garments, the priest's daily service physically connected every layer of creation [רבנו בחיי].