Exodus 28:36-38

36“You are to make a pure gold medallion and engrave it, like the engraving of a seal: Holy to the Lord.

37Fasten it to a cord of blue yarn so it can be placed on the turban; the medallion is to be on the front of the turban.

38It will be on Aaron’s forehead so that Aaron may bear the guilt connected with the holy offerings that the Israelites consecrate as all their holy gifts. It is always to be on his forehead, so that they may find acceptance with the Lord.