A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
exo 28:1APPOINTMENT TO THE PRIESTHOOD. (Exo. 28:1-43)
take thou unto thee Aaron thy brother, and his sons with him--Moses had hitherto discharged the priestly functions (Psa 99:6), and he evinced the piety as well as humility of his character, in readily complying with the command to invest his brother with the sacred office, though it involved the perpetual exclusion of his own family. The appointment was a special act of God's sovereignty, so that there could be no ground for popular umbrage by the selection of Aaron's family, with whom the office was inalienably established and continued in unbroken succession till the introduction of the Christian era.
exo 28:2holy garments--No inherent holiness belonged either to the material or the workmanship. But they are called "holy" simply because they were not worn on ordinary occasions, but assumed in the discharge of the sacred functions (Eze 44:19).
for glory and for beauty--It was a grand and sumptuous attire. In material, elaborate embroidery, and color, it had an imposing splendor. The tabernacle being adapted to the infantine aid of the church, it was right and necessary that the priests' garments should be of such superb and dazzling appearance, that the people might be inspired with a due respect for the ministers as well as the rites of religion. But they had also a further meaning; for being all made of linen, they were symbolical of the truth, purity, and other qualities in Christ that rendered Him such a high priest as became us.
exo 28:6ephod--It was a very gorgeous robe made of byssus, curiously embroidered, and dyed with variegated colors, and further enriched with golden tissue, the threads of gold being either originally interwoven or afterwards inserted by the embroiderer. It was short--reaching from the breast to a little below the loins--and though destitute of sleeves, retained its position by the support of straps thrown over each shoulder. These straps or braces, connecting the one with the back, the other with the front piece of which the tunic was composed, were united on the shoulder by two onyx stones, serving as buttons, and on which the names of the twelve tribes were engraved, and set in golden encasements. The symbolical design of this was, that the high priest, who bore the names along with him in all his ministrations before the Lord, might be kept in remembrance of his duty to plead their cause, and supplicate the accomplishment of the divine promises in their favor. The ephod was fastened by a girdle of the same costly materials, that is, dyed, embroidered, and wrought with threads of gold. It was about a handbreadth wide and wound twice round the upper part of the waist; it fastened in front, the ends hanging down at great length (Rev 1:13).
exo 28:15thou shalt make the breastplate of judgment with cunning work--a very splendid and richly embroidered piece of brocade, a span square, and doubled, to enable it the better to bear the weight of the precious stones in it. There were twelve different stones, containing each the name of a tribe, and arranged in four rows, three in each. The Israelites had acquired a knowledge of the lapidary's art in Egypt, and the amount of their skill in cutting, polishing, and setting precious stones, may be judged of by the diamond forming one of the engraved ornaments on this breastplate. A ring was attached to each corner, through which the golden chains were passed to fasten this brilliant piece of jewelry at the top and bottom tightly on the breast of the ephod.
exo 28:30thou shalt put in the breastplate of judgment the Urim and Thummim--The words signify "lights" and "perfections"; and nothing more is meant than the precious stones of the breastplate already described (compare Exo 39:8-21; Lev 8:8). They received the name because the bearing of them qualified the high priest to consult the divine oracle on all public or national emergencies, by going into the holy place--standing close before the veil and putting his hand upon the Urim and Thummim, he conveyed a petition from the people and asked counsel of God, who, as the Sovereign of Israel, gave response from the midst of His glory. Little, however, is known about them. But it may be remarked that Egyptian judges wore on the breast of their official robes a representation of Justice, and the high priest in Israel long officiated also as a judge; so that some think the Urim and Thummim had a reference to his judicial functions.
exo 28:31the robe of the ephod all of blue--It was the middle garment, under the ephod and above the coat. It had a hole through which the head was thrust, and was formed carefully of one piece, such as was the robe of Christ (Joh 19:23). The high priest's was of a sky-blue color. The binding at the neck was strongly woven, and it terminated below in a fringe, made of blue, purple, and scarlet tassels, in the form of a pomegranate, interspersed with small bells of gold, which tinkled as the wearer was in motion.
exo 28:34a golden bell and a pomegranate--The bells were hung between the pomegranates, which were said to have amounted to seventy-two, and the use of them seems to have been to announce to the people when the high priest entered the most holy place, that they might accompany him with their prayers, and also to remind himself to be attired in his official dress, to minister without which was death.
exo 28:36plate--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.
exo 28:37mitre--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.
exo 28:39coat of fine linen--a garment fastened at the neck, and reaching far down the person, with the sleeves terminating at the elbow.
girdle of needlework--a piece of fine twined linen, richly embroidered, and variously dyed. It is said to have been very long, and being many times wound round the body, it was fastened in front and the ends hung down, which, being an impediment to a priest in active duty, were usually thrown across the shoulders. This was the outer garment of the common priests.
exo 28:42linen breeches--drawers, which encompassed the loins and reached half way down the thighs. They are seen very frequently represented in Egyptian figures.