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Source:Martin Harris:EMD 2:338:no man ever heard me in any way deny the truth of the Book of Mormon
Martin Harris (1871): "No man ever heard me in any way deny the truth of the Book of Mormon"
Martin Harris wrote the following in a letter to Hanna B. Emerson in January 1871:
I answer emphatically, No, I did not;—no man ever heard me in any way deny the truth of the Book of Mormon, the administration of the angel that showed me the plates; nor the organization of the Church of Jesus Christ of Latter Day Saints, under the administration of Joseph Smith Jun., the prophet whom the Lord raised up for that purpose, in these the latter days, that he may show forth his power and glory. The Lord has shown me these things by his Spirit—by the administration of holy angels—and confirmed the same with signs following, step by step, as the work has progressed, for the space of fifty-three years. 
- Letter of Martin Harris, Sr., to Hanna B. Emerson, Smithfield, Utah Territory, in Early Mormon Documents, 2: 338.