Exodus 28:36-38

“Make a plate of pure gold. Engrave on it as on a seal: ‘Holy to GOD.’ Tie it with a blue cord to the front of the turban. It is to rest there on Aaron’s forehead. He’ll take on any guilt involved in the sacred offerings that the Israelites dedicate, no matter what they bring. It will always be on Aaron’s forehead so that the offerings will be acceptable before GOD.