An ancient instrument or tool prepared by God and used by Joseph Smith to aid in the translation of the Book of Mormon. God provided a Urim and Thummim to His prophets in ancient times (see Exodus 28:30; 1 Samuel 28:6; Ezra 2:63).
“The Contributions of Martin Harris,” Church History
“Pennsylvania: Priesthood Restoration Site, Harmony (now Oakland),” Church History
“The Experience of the Three Witnesses,” Church History
Richard E. Turley Jr., Robin S. Jensen, and Mark Ashurst-McGee, “Joseph the Seer,” Ensign, October 2015
Gerrit Dirkmaat, “Great and Marvelous Are the Revelations of God,” Ensign, January 2013
“Coming Forth of the Book of Mormon,” Friend, September 2004
H. Donl Peterson, “Moroni—Joseph Smith’s Tutor,” Ensign, January 1992