The high priest's ankle-length Robe was worn under the Ephod and Breastplate. The bottom seam of this Robe was adorned all around with small golden bells and woolen pomegranates.
G-d told Moses, "The Robe must be worn by Aaron in order [for him] to serve [as high priest]."
The unity of the Jewish people was reflected in the three primary garments of the high priest:
The names of the tribes that were engraved on the Breastplate, resting on the high priest's heart, signified the righteous among us.
The names of the tribes that were engraved on the stones of the Ephod, which mainly covered the high priest's back, signified formerly estranged Jews who have returned to Jewish observance.
The bells and pomegranates of the Robe signified those Jews still struggling with their evil inclinations.
All of these Jews must be represented when the high priest enters the Sanctuary, for he must invoke the merit that is common to all his people.
Similarly, when we see people in need of a spiritual boost, we must first make them aware of their inherent worth: that they possess a soul that is truly a part of G-d. By welcoming them back into Jewish observance, we can help them shed whatever negativity remains in their lives and increases their performance of deeds of light and goodness.
From Daily Wisdom