Hyrum Smith writes to Brigham Young and explains the recent great excitement around Nauvoo with the mass meetings by mobs drawing up resolutions to "utterly exterminate the Saints." He recommends that the Twelve return without delay and advises, "A word to the wise is sufficient; and a little powder, lead and a good rifle can be packed in your luggage very easy without creating any suspicion."
Joseph and 15 others are arrested on this day on the charge of "riot." They appear before Daniel H. Wells (who will later be baptized) and are discharged. Stephen Markham brings warning that mobs are joining together all around Nauvoo in preparation to attack. Joseph notifies both the police and the Nauvoo Legion to be prepared. He hears a rumor that the Law brothers will try to burn the Nauvoo Neighbor office this night, so a strong police force is placed on the premise.
[Conkling, Christopher J., Joseph Smith Chronology]