Smith's Bible Dictionary
High Priest. (Hebrew, cohen), priest. The first distinct separation of Aaron to the office of the priesthood, which previously belonged to the first-born was that recorded Exodus 28:1. We find from the very first, the following characteristic attributes of Aaron and the high priests his successors, as distinguished from the other priests: Aaron alone was anointed, Leviticus 8:12, whence one of the distinctive epithets of the high priest was "the anointed priest". Leviticus 4:3; Leviticus 4:5; Leviticus 4:16; Leviticus 21:10. See Numbers 35:25. The anointing of the sons of Aaron, that is, The common priests seems to have been confined to sprinkling their garments with the anointing oil. Exodus 29:21; Exodus 28:41; etc.
The high priest had a peculiar dress, which passed to his successor at his death. This dress consisted of eight parts:
(a) The breastplate, or, as it is further named, vs. Exodus 28:15; Exodus 28:29-30, the breastplate of judgment. The breastplate was originally two spans long and one span broad, but when doubled it was square, the shape in which it was worn. On it were the twelve precious stones, set in four rows, three in a row, thus corresponding to the twelve tribes - each stone having the name of one of the children of Israel engraved upon it.
(b) The ephod. This consisted of two parts, of which one covered the back and the other the front, that is, The breast and upper part of the body. These parts were clasped together on the shoulder with two large onyx stones, each having engraved on it six of the names of the tribes of Israel. They were further united by a "curious girdle" of gold blue purple, scarlet and fine twined linen round the waist. See Ephod; Girdle.
(c) The robe of the ephod. This was of inferior material to the ephod itself being all of blue, Exodus 28:31, which implied its being only of "woven work." Exodus 39:22. It was worn immediately under the ephod, and was longer than it. The skirt of this robe had a remarkable trimming of pomegranates in blue, red and crimson, with a bell of gold between each pomegranate alternately. The bells were to give a sound when the high priest went in and came out of the Holy Place.
(d) The mitre or upper turbin, with its gold plate, engraved with "Holiness to the Lord", fastened to it by a ribbon of blue.
(e) The broidered coat was a tunic or long skirt of linen with a tessellated or diaper pattern, like the setting of stone.
(f) The girdle, also of linen, was wound round the body several times from the breast downward, and the ends hung down to the ankles.
(g) The breeches or drawers, of linen, covered the loins and thighs; and
(h) The bonnet was a turban of linen, partially covering the head, but not in the form of a cone like that of the high priest when the mitre was added to it. These last four were common to all priests.
The high priest alone was permitted to enter the Holy of Holies, which he did once a year, on the Great Day of Atonement, when he sprinkled the blood of the Sin Offering on the mercy seat, and burnt incense within the veil. Leviticus 16:1. The accidental manslayer might not leave the City of Refuge during the lifetime of the existing high priest. It was also forbidden to the high priest to follow a funeral, or rend his clothes for the dead.
It does not appear by whose authority the high priests were appointed to their office before there were kings of Israel. After this, the office seems to have been used for political rather than religious purposes. Though at first, chosen for life, we find that Solomon deposed Abiathar, 1 Kings 2:35, and that Herod appointed a number of high priests, which may account for there being at least two living in Christ's time, Annas and Caiaphas. Luke 3:2.
The usual age for entering upon the functions of the priesthood, according to 2 Chronicles 31:17 is considered to have been 20 years, though a priest or high priest was not actually incapacitated if he had attained to puberty. Again, according to Leviticus 21:17-21 no one that had a blemish could officiate at the altar.
The theological view of the high priesthood does not fall within the scope of this work. It must suffice, therefore, to indicate that such a view would embrace the consideration of the office, dress, functions and ministrations of the high priest considered as typical of the priesthood of our Lord Jesus Christ, and as setting forth under shadows the truths which are openly taught under the gospel. This had been done to a great extent in the Epistle to the Hebrews. It would also embrace all the moral and spiritual teaching supposed to be intended by such symbols.
These files are public domain.
Smith, William, Dr. Entry for 'High Priest'. Smith's Bible Dictionary. https://www.studylight.org/dictionaries/eng/sbd/h/high-priest.html. 1901.