Exodus 28:33-35

Make balls like pomegranates of blue, purple, and red thread, and hang them around the bottom of the outer robe with gold bells between them. All around the bottom of the outer robe there should be a gold bell and a pomegranate ball, a gold bell and a pomegranate ball. Aaron must wear this robe when he serves as priest. The ringing of the bells will be heard when he enters and leaves the Holy Place before the LORD so that Aaron will not die.