And thou shalt put it on a blue lace, that it may be upon the mitre; upon the forefront of the mitre it shall be.

Jamieson-Fausset-Brown Bible Commentary

37. mitre-crown-like cap for the head, not covering the entire head, but adhering closely to it, composed of fine linen. The Scripture has not described its form, but from Josephus we may gather that it was conical in shape, as he distinguishes the mitres of the common priests by saying that they were not conical-that it was encircled with swathes of blue embroidered, and that it was covered by one piece of fine linen to hide the seams.

Matthew Henry's Concise Commentary

28:31-39 The robe of the ephod was under the ephod, and reached down to the knees, without sleeves. Aaron must minister in the garments appointed. We must serve the Lord with holy fear, as those who know they deserve to die. A golden plate was fixed on Aaron's forehead, engraven with Holiness to the Lord. Aaron was hereby reminded that God is holy, and that his priests must be holy, devoted to the Lord. This must appear in their forehead, in open profession of their relation to God. It must be engraven like the engravings of a signet; deep and durable; not painted so as to be washed off, but firm and lasting; such must our holiness to the Lord be. Christ is our High Priest; through him sins are forgiven to us, and not laid to our charge. Our persons, our doings, are pleasing to God upon the account of Christ, and not otherwise.