=14.= At a subsequent period of Israel's history, the Lord chose the tribe of Levi to assist Aaron in the priestly functions, the special duties of the Levites being to keep the instruments and attend to the service of the tabernacle. The Levites thus chosen of the Lord were to take the place of the first-born throughout the tribes, whom the Lord had claimed for His service from the time of the last dread plague in Egypt, whereby the first-born in every Egyptian house was slain, while the eldest in every Israelitish house was hallowed and spared.[626] The commission thus given to the Levites is sometimes called the _Levitical Priesthood_;[627] it is to be regarded as an appendage to the priesthood of Aaron, not comprising the highest priestly powers. The Aaronic Priesthood, as restored to the earth in this dispensation, comprises the Levitical order.[628] This priesthood holds the keys of the ministering of angels, and the authority to attend to the outward ordinances, the letter of the gospel;[629] it comprises the offices of deacon, teacher, and priest, with the bishopric holding the keys of presidency. [626] Numb. iii, 12-13, 39, 44-45, 50-51. [627] Heb. vii, 11. [628] Doc. and Cov. cvii, 1. [629] Doc. and Cov. cvii, 20. =15.= The greater or _Melchizedek Priesthood_ is named after the king of Salem, a great High Priest of God;[630] before his day it was known as "the Holy Priesthood, after the order of the Son of God, but out of respect or reverence to the name of the Supreme Being, to avoid the too frequent repetition of His name, they, the Church, in ancient days, called that Priesthood after Melchizedek."[631] This priesthood holds the right of presidency in all the offices of the Church; its special functions lie in the administration of spiritual things: comprising as it does the keys of all spiritual blessings of the Church, the right "to have the heavens opened unto them, to commune with the general assembly and Church of the First Born, and to enjoy the communion and presence of God the Father, and Jesus the Mediator of the new covenant."[632] The special offices of the Melchizedek Priesthood are those of apostle, patriarch or evangelist, high priest, seventy, and elder. Revelation from God has defined the duties associated with each of these callings; and the same high authority has directed the establishment of presiding officers growing out of, or appointed from among those who are ordained to the several offices in these two priesthoods.[633] [630] Gen. xiv, 18; Heb. vii, 1-17. [631] Doc. and Cov. cvii, 2-4. [632] Doc. and Cov. cvii, 8, 18-19. [633] Doc. and Cov. cvii, 21.