Charles Ellicott Commentary Exodus 29:6

"and thou shalt set the mitre upon his head, and put the holy crown upon the mitre." — Exodus 29:6 (ASV)

The holy crown. —The golden plate, inscribed with Holiness to the Lord, and attached to the mitre by a lace or ribbon, resembled the “diadems” worn in the East by monarchs, and regarded as the main emblem of their sovereignty. In Egypt, such a diadem is found first in the reign of Amenôphis IV (Khuenaten), the ninth king of the eighteenth dynasty. The assignment of a crown to the high priest gave him that quasi-royal dignity which marked him as a type of our Lord in His threefold office of Prophet, Priest, and King.