"This ordination gave the two men authority to baptize (see Baptism), and they immediately performed that ordinance for one another in the Susquehannah River. The Prophet Joseph Smith had received no previous revelations authorizing him to baptize; to perform that ordinance properly required specific authorization from God. The return of John to bestow the Aaronic Priesthood confirmed that divine authority had been lost from the earth and that a heavenly visitation was necessary to restore it."

(Encyclopedia of Mormonism, 1-4 vols., edited by Daniel H. Ludlow (New York: Macmillan, 1992), 3, "Aaronic Priesthood")