2 Ne. 31:8
“The sign of the dove was instituted before the creation of the world, a witness for the Holy Ghost… . The Holy Ghost is a personage, and is in the form of a personage It does not confine itself to the form of the dove, but in sign of the dove. The Holy Ghost cannot be transformed into a dove; but the sign of a dove was given to John to signify the truth of the deed, [Christ’s baptism] as the dove is an emblem or token of truth and innocence.” (Joseph Smith, History of the Church, 5:260-261)