Exodus 28:36-38 - The Turban
36 "You are to make a plate of pure gold and engrave on it the way a seal is engraved: "Holiness to the Lord."
37 You are to attach to it a blue cord so that it will be on the turban; it is to be on the front of the turban, 38 It will be on Aaron's forehead, and Aaron will bear the iniquity of the holy things, which the Israelites are to sanctify by all their holy gifts; it will always be on his forehead, for their acceptance before the Lord.