“The Source of Priesthood Authority,” Ensign, March 2019
The priesthood is the power and authority of God, which He gives to us to help carry out His work of salvation (see Handbook 2: Administering the Church , page 8). The Lord has given His priesthood to chosen servants since the days of Adam. Because the priesthood is given to worthy men by the laying on of hands and a record is kept of those ordinations, priesthood holders today can trace their line of authority back to Joseph Smith, who received the Melchizedek Priesthood from Apostles of Jesus Christ.
During His mortal ministry, Jesus Christ gave His priesthood authority to His Apostles, including Peter, James, and John (see Matthew 10).
On May 15, 1829, John the Baptist appeared to Joseph Smith and Oliver Cowdery to give them the Aaronic Priesthood. A few weeks later, the ancient Apostles Peter, James, and John gave Joseph Smith and Oliver Cowdery the Melchizedek Priesthood (see Doctrine and Covenants 27:12; 128:20; Teachings of the Prophet Joseph Smith, sel. Joseph Fielding Smith , 81, 101).
The Prophet Joseph Smith gave the priesthood to other worthy men, who, under the Prophet’s direction, gave it to other worthy men, and so on, up to the modern day.
Priesthood keys are the authority God has given to priesthood leaders to direct the use of His priesthood on earth, including how the priesthood is passed from one priesthood holder to another. For example, only a bishop, who holds the priesthood keys for his ward, can authorize a man or young man in his ward to receive the Aaronic Priesthood. In April 1836 the Prophet Joseph Smith received important priesthood keys from Moses, Elias, and Elijah in the Kirtland Temple (see Doctrine and Covenants 110).