Mention of oath by Heber C. Kimball during a priesthood meeting and recorded in the journal of William Clayton:
[Heber C. Kimball] said the Twelve would have to leave shortly, for a charge of treason would be brought against them for swearing us to avenge the blood of the anointed ones, and some one would reveal it and we shall have to part some say between sundown and dark. . . . [He also said] I have covenanted, and never will rest nor my posterity after me until those men who killed Joseph and Hyrum have been wiped out of the earth.
[George D. Smith, An Intimate Chronicle: The Journals of William Clayton (Salt Lake City: Signature Books, 1995), 223–24, as quoted in Sources on the Oath of Vengeance or Law of Retribution, Christopher C. Smith, privately circulated]