Benjamin F. Johnson remembers Joseph telling him and his (Johnson's) mother about plural marriage; said an angel commanded him to practice it; that he slept with sister Almera "as man and wife."
"Testimony of Benjamin F. Johnson," Affidavits about celestial marriage, 1869-1915, MS 3423, Church History Library
After a short period, President Smith and company, viz. George Miller, William Clayton, J. M. Smith, and Ezlia and Lydia Emily Partridge, (who were the wives of the Prophet) came again to Macedonia (Ramus) where he reamined two days, lodging at my house with my sister, as man and wife. (And to my certain knowledge he occupied the same bed with her.) This visit was on the Sixteenth and Seventeenth of May, eighteen-hundred and forty-three, returning to Nauvoo on the eighteenth.
. . .
He [Joseph Smith] also visited my mother [Julia E. Hills] at her residence in Macedonia [Illinois], and taught her in my hearing, the doctrine of Celestial marriage, declairing that an Angel appeared unto him with a drawn Sword, threatening to slay him if he did not proceed to fulfill the law that had been given to him, and counselled my mother to be sealed to his uncle, Father John Smith, to which she consented, and to my certain knowledge was subsequently sealed to him by the Prophet.