13. Ordination of Joseph Smith and Oliver Cowdery to the Aaronic Priesthood on the banks of the Susquehanna River near Harmony, Pennsylvania, May 15, 1829.

Doctrine and Covenants of the Church of Jesus Christ of the Latter-Day Saints, at sacred-texts.com

13. Ordination of Joseph Smith and Oliver Cowdery to the Aaronic Priesthood on the banks of the Susquehanna River near Harmony, Pennsylvania, May 15, 1829.
History of the Church 1:39-42.

13:1 Upon you my fellow servants, in the name of Messiah I confer the Priesthood of Aaron, which holds the keys of the ministering of angels, and of the gospel of repentance, and of baptism by immersion for the remission of sins; and this shall never be taken again from the earth, until the sons of Levi do offer again an offering unto the Lord in righteousness.