Aaronic Priesthood – by age 12

Encyclopedia of Mormonism

The Aaronic Priesthood – The two divisions of priesthood in The Church of Jesus Christ of Latter-day Saints are the Aaronic and the Melchizedek. Young men twelve to eighteen years of age, and older men who are new converts, are ordained to offices in the Aaronic Priesthood, "which holds the keys [governing or delegating authority] of the ministering of angels, and of the gospel of repentance, and of baptism by immersion for the remission of sins" (D&C 13). It is the priesthood authority by which John the Baptist prepared the way for Jesus Christ, teaching faith, repentance, and baptism for the remission of sins (Matt. 3:1-17; Mark 1:1-11; Luke 1:5-80; John 1:15-34; Acts 8:14-17; D&C 84:25-28). The Aaronic Priesthood does not have the power to confer the Holy Ghost (Matt. 3:11; Mark 1:7-8; John 1:33-34; JS-H 1:70) or to administer totally the affairs of the kingdom of God. It is power and authority God has given to man to prepare him and those to whom he ministers to receive the greater power, authority, and blessings of the Melchizedek Priesthood.