And thou shalt make a plate of pure gold, and grave upon it, like the engravings of a signet, {o} HOLINESS TO THE LORD.

(o) Holiness belongs to the Lord: for he is most holy, and nothing unholy may appear before him.

Wesley's Notes

28:36 On the golden plate fixed upon Aaron's forehead, like an half coronet, reaching, as the Jews say, from ear to ear, must be engraven, Holiness to the Lord - Aaron must hereby be minded, that God is holy, and that his priests must be holy. The high priest must be consecrated to God, and so must all his ministrations. All that attend in God's house must have holiness to the Lord engraven upon their foreheads, that is, they must he holy, devoted to the Lord, and designing his glory in all they do. This must appear in their forehead, in an open profession of their relation to God, as those that are not ashamed to own it, and in a conversation answerable to it. It must likewise be engraven like the engravings of a signet, so deep, so durable; not painted, so as it may he washed off, but sincere and lasting.

Jamieson-Fausset-Brown Bible Commentary

36-38. plate-literally, a petal of a flower, which seems to have been the figure of this golden plate, which was tied with a ribbon of blue on the front of the mitre, so that every one facing him could read the inscription.

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.