“You shall make on its hem pomegranates of turquoise, purple, and scarlet wool, on its hem all around, and gold bells between them all around.” (Exodus 28:33)
This hem of alternating bells and pomegranates was certainly one of the more unusual features of the High Priest’s garments. What was the purpose of the bells?
Two verses later we are told that they were there so that “its sound will be heard as he approaches the holy place.”
Ramban explains that proper manners dictate that one announce oneself before entering a room. In fact, based on this lesson from the bells of the High Priest, Rabbi Akiva instructed his son that even when entering his own home, he should not do so unexpectedly, but first knock or let people know that he’s about to enter.