On its hem you shall make pomegranates of blue and purple and scarlet yarns, around its hem, with bells of gold between them, a golden bell and a pomegranate, a golden bell and a pomegranate, around the hem of the robe.
#exodus 28:33-34

Perhaps in order for God to bless us (pomegranates) he needs a way to drown out our complaining (bells). Of course, the ornaments on the priest's uniform are only symbolic. They can't actually have any effect on God's ability to hear our nonsense... Can they?
#tetzaveh