Easton's Bible Dictionary
To the high priest alone it was permitted to enter the holy of holies, which he did only once a year, on the great Day of Atonement, for "the way into the holiest of all was not yet made manifest" (Hebrews 9; 10 ). Wearing his gorgeous priestly vestments, he entered the temple before all the people, and then, laying them aside and assuming only his linen garments in secret, he entered the holy of holies alone, and made expiation, sprinkling the blood of the sin offering on the mercy seat, and offering up incense. Then resuming his splendid robes, he reappeared before the people (Leviticus 16 ). Thus the wearing of these robes came to be identified with the Day of Atonement.
The office, dress, and ministration of the high priest were typical of the priesthood of our Lord (Hebrews 4:14; 7:25; 9:12 , etc.).
It is supposed that there were in all eighty-three high priests, beginning with Aaron (B.C. 1657) and ending with Phannias (A.D. 70). At its first institution the office of high priest was held for life (but Compare 1 Kings 2:27 ), and was hereditary in the family of Aaron (Numbers 3:10 ). The office continued in the line of Eleazar, Aaron's eldest son, for two hundred and ninety-six years, when it passed to Eli, the first of the line of Ithamar, who was the fourth son of Aaron. In this line it continued to Abiathar, whom Solomon deposed, and appointed Zadok, of the family of Eleazar, in his stead (1 Kings 2:35 ), in which it remained till the time of the Captivity. After the Return, Joshua, the son of Josedek, of the family of Eleazar, was appointed to this office. After him the succession was changed from time to time under priestly or political influences.
These dictionary topics are from M.G. Easton M.A., D.D., Illustrated Bible Dictionary, Third Edition, published by Thomas Nelson, 1897. Public Domain.
Easton, Matthew George. Entry for 'High Priest'. Easton's Bible Dictionary. https://www.studylight.org/dictionaries/eng/ebd/h/high-priest.html. 1897.