See Aaron, Aaronites, Bishops, Deacons, John the Baptist, Keys, Law of Moses, Levites, Melchizedek Priesthood, Ordinations, Priesthood, Priesthood of Elias, Priesthood Offices, Priesthood Quorums, Priests, Quorum Presidents, Teachers.
When the Lord first gave the law of carnal commandments, the preparatory gospel, to school Israel for a future time when again they could enjoy the gospel fulness, of necessity a lesser order of priesthood was conferred to administer the lesser law. (Heb. 7:12; Inspired Version, Ex. 34:1-2.) This lesser priesthood (D. & C. 85:11) was conferred upon Aaron and his sons after him (Ex. 28; 29; 30; Lev. 1:11; 3:2; 13:2; Num. 18), as “an everlasting priesthood throughout their generations.” (Ex. 40:15; Num. 25:10-13) It was also conferred upon substantially the whole house of Levi who were between 30 and 50 years of age. (Num. 3; 4.) Hence it is called the Aaronic or Levitical Priesthood; the two names are synonymous. (D. & C. 107:1, 6, 10.)
Aaron and his sons after him held the keys of the Aaronic Priesthood and acted in the full majesty and power of this Levitical order; many of their functions were comparable to those of bishops and priests in this dispensation. Though the rest of the ordained Levites held the fulness of the Aaronic Priesthood (Heb. 7:5) and participated in the offering of sacrifices, they did not hold the keys of the Aaronic ministry; many of their functions were comparable to those of teachers and deacons in this dispensation.(Num. 3; 4.; 2 Chron. 29; Mal. 3:3; D. & C. 13; Doctrines of Salvation, vol. 3, pp. 111-114.)
From Aaron to John the Baptist the hereditary nature of the Levitical Priesthood “was in active operation.” (Teachings, pp. 318-319; D & C 84:18, 26-27, 30; 107:13.) This priesthood in that day was conferred solely upon worthy members of the special lineage chosen to receive it; it came to individuals by descent, because of father and because of mother, as contrasted with the Melchizedek Priesthood which was “without father, without mother, without descent.” (Heb. 7:3.) John the Baptist “was a descendant of Aaron” and held the keys of the Aaronic Priesthood. (Teachings, pp. 272-273.) There was no Aaronic Priesthood among the Nephites prior to the ministry of the resurrected Lord among them, for none of the tribe of Levi accompanied the Nephite peoples to their promised land.
Few members of the tribe of Levi gathered with the fold of Israel in the meridian of time; few have come back to the fold of their fathers in this dispensation; and there were none among the Nephites to whom our Lord ministered. Consequently, beginning in the day of the primitive Church the lesser priesthood was spread out among the body of the people and was no longer confined exclusively to the chosen lineage. When the latter-day kingdom is perfected, and when the other tribes of Israel are gathered and receive their blessings under the hands of Ephraim, the first to gather (D. & C. 133:26-35), then the sons of Levi again will stand forth in the majesty of their calling and “offer again an offering unto the Lord in righteousness.” (D. & C. 13.)
John the Baptist, as a resurrected personage, came to Joseph Smith and Oliver Cowdery on the 15th of May, 1829, and made the first conferral of Levitical Priesthood in this dispensation. (D. & C. 13; 27:8.) Since then, as the needs of the ministry warranted, the offices of bishop, priest,teacher, and deacon, have all been revealed as part of this Aaronic ministry.
The Priesthood of Aaron “is called the lesser priesthood . . . because it is an appendage to the greater, or the Melchizedek Priesthood, and has power in administering outward ordinances.” (D. & C. 107:13-14.) Though it is a lesser priesthood, it is yet one of great majesty and power. It holds “the keys of the ministering of angels,” meaning that those who hold it and are faithful have the key whereby they can open the door to the receipt of visitations from heavenly messengers. (D. & C. 13; 84:26-27; 107:20.) Faith, repentance, and baptism comprising as they do the preparatory gospel—fall within its province, though the laying on of hands for the gift of the Holy Ghost is not a prerogative that attends it.
Perfection does not come by the Levitical order, and this lesser priesthood is not received with an oath. (Heb. 7:11, 21; Teachings, p. 323.) But it is a preparatory priesthood, the Priesthood of Elias, the schooling ministry, which prepares its worthy and faithful ministers for the oath and covenant and perfection that appertain to the Melchizedek order. That those who train themselves to receive the Melchizedek Priesthood, by magnifying their callings in the Aaronic Priesthood, must be true and faithful and worthy for the final receipt of the greater priesthood is self evident. Indeed, one of the reasons the Lord destroyed Korah and his band of Levites was that they, being unworthy, sought “the high priesthood also.” (Inspired Version, Num. 16.)