Exodus 28:36-38

“You shall also make a plate of pure gold and shall engrave on it, like the engravings of a seal, ‘Holy to the LORD.’ You shall fasten it on a blue cord, and it shall be on the turban; it shall be at the front of the turban. It shall be on Aaron’s forehead, and Aaron shall take away the iniquity of the holy things which the sons of Israel consecrate, with regard to all their holy gifts; and it shall always be on his forehead, that they may be accepted before the LORD.