Exodus 28:33-35

33Make pomegranates of blue, purple and scarlet yarn around the hem of the robe, with gold bells between them. 34The gold bells and the pomegranates are to alternate around the hem of the robe.

35Aaron must wear it when he ministers. The sound of the bells will be heard when he enters the Holy Place before the LORD and when he comes out, so that he will not die.