Martha Brotherton, a young Nauvoo woman, was allegedly approached by Brigham Young in Joseph Smith's private office. "Were it lawful and right," Brotherton reported Young as saying, "could [you] accept of me for your husband and companion? . . . Brother Joseph has had a revelation from God that it is lawful and right for a man to have two wives; for as it was in the days of Abraham, so it shall be in these last days . . . if you will accept of me, I will take you straight to the celestial kingdom." Brigham then left the room and returned ten minutes later with the Prophet. "Just go ahead, and do as Brigham wants you to," Brotherton reported Smith as saying. "I know that this is lawful and right . . . I have the keys of the kingdom, and whatever I bind on earth is bound in heaven, and whatever I loose on earth is loosed in heaven." Martha noted she begged for time to consider, then left for Saint Louis, where she published her story in the 15 July 1842 St. Louis Bulletin.
[Source: St. Louis Bulletin, 15 July 1842; in Joseph Smith Polygamy Timeline, http://www.i4m.com/think/polygamy/JS_Polygamy_Timeline.htm]