Be it known unto all nations, kindreds, tongues, and people, unto whom this work shall come: That we, through the grace of God the Father, and our Lord Jesus Christ, have seen the plates which contain this record, which is a record of the people of Nephi, and also of the Lamanites, their brethren, and also of the people of Jared, who came from the tower of which hath been spoken. And we also know that they have been translated by the gift and power of God, for his voice hath declared it unto us; wherefore we know of a surety that the work is true. And we also testify that we have seen the engravings which are upon the plates; and they have been shown unto us by the power of God, and not of man. And we declare with words of soberness, that an angel of God came down from heaven, and he brought and laid before our eyes, that we beheld and saw the plates, and the engravings thereon; and we know that it is by the grace of God the Father, and our Lord Jesus Christ, that we beheld and bear record that these things are true. And it is marvelous in our eyes. Nevertheless, the voice of the Lord commanded us that we should bear record of it; wherefore, to be obedient unto the commandments of God, we bear testimony of these things. And we know that if we are faithful in Christ, we shall rid our garments of the blood of all men, and be found spotless before the judgment-seat of Christ, and shall dwell with him eternally in the heavens. And the honor be to the Father, and to the son, and to the Holy Ghost, which is one God. Amen.

OLIVER COWDERY DAVID WHITMER MARTIN HARRIS

The importance of the Three Witnesses.
President Dallin H. Oaks explained why the testimony of the Three Witnesses is so compelling:

“The testimony of the Three Witnesses to the Book of Mormon stands forth in great strength. Each of the three had ample reason and opportunity to renounce his testimony if it had been false, or to equivocate on details if any had been inaccurate. As is well known, because of disagreements or jealousies involving other leaders of the Church, each one of these three witnesses was excommunicated from The Church of Jesus Christ of Latter-day Saints by about eight years after the publication of their testimony. All three went their separate ways, with no common interest to support a collusive effort. Yet to the end of their lives—periods ranging from 12 to 50 years after their excommunications—not one of these witnesses deviated from his published testimony or said anything that cast any shadow on its truthfulness” (“The Witness: Martin Harris,” Ensign, May 1999, 36).


The testimony of John Whitmer.
John Whitmer, one of the Eight Witnesses of the Book of Mormon, declared: “I have never heard that any one of the three or eight witnesses ever denied the testimony that they have borne. … Our names have gone forth to all nations, tongues and people as a divine revelation from God. And it will bring to pass the designs of God according to the declaration therein contained” (in Noel B. Reynolds, ed., Book of Mormon Authorship Revisited: The Evidence for Ancient Origins [1997], 55–56).

Overview of Three Witnesses.
On Sunday, June 28, 1829,[6][7] Joseph Smith, Oliver Cowdery, David Whitmer, and Martin Harris went into the woods near the home of Peter Whitmer, Sr. ( Vogel, p. 9.; Bushman, Richard Lyman, Joseph Smith: Rough Stone Rolling, New York: Alfred A. Knopf, 2005, p. 78. ; Manuscript History, A-2:26, in Selected Collections, Vol. 1, DVD #1, MH8_29.; History of the Church, 1:54._ ) and prayed to receive a vision of the golden plates. After some time, Harris left the other three men, believing his presence had prevented the vision from occurring. The remaining three again knelt and said they soon saw a light in the air overhead and an angel holding the golden plates. Smith retrieved Harris, and after praying at some length with him, Harris too said he saw the vision.[12]

While there are various second hand accounts that each denied the account of seeing an angel and holding the plates, these are all second hand and are hard to verify. One might suppose that in moments of great in-difference with Joseph Smith each may have said some things to hurt Joseph Smith. So the idea that they might have said things that disagreed with their original statements, well they are men. To me you have to come to their individual verified statements given at their times of death, they would mena the most to me when they had nothing to lose or gain from their statements. ( Givens, Terryl (2009), The Book of Mormon: a very short introduction, Oxford University Press, p. 99 ("the three witnesses all defected from Smith and his church, (only Whitmer permanently), though all maintained until death the truth of the affidavits." In 1838, Joseph Smith called Cowdery, Harris, and Whitmer "too mean to mention; and we had liked to have forgotten them." B.H. Roberts, ed. History of the Church (Salt Lake City: Deseret News, 1905), 3: 232. Technically, Whitmer resigned before the High Council decided that he "be no longer considered a member of the Church of Christ of Latter day Saints." Ronald E. Romig, "Faithful Dissenter, Witness Apart," in Roger D. Launius and Linda Thatcher, Dissenting Visions: Dissenters in Mormon History (Urbana: University of Illinois Press, p. 36; Michael Marquardt, "David Whitmer: His Evolving Beliefs and Recollections," in Scattering of the Saints, Schism within Mormonism, eds. Newell G. Bringhurst and John C. Hamer, (Independence, MO: John Whitmer Books, 2007) p. 50.

The overall feeling of the day by those who considered themselves christian was that it would have been impossible or anyone to receive a divine visitation. The reasoning was based on the stories from the Bible that instructed that those who looked upon the Ark of The Covenant without proper authorization were destroyed by God. That God had to hide his presence from Man or they would be burnt up. The people were protected at the time of Moses as there were clouds on the mountain when Moses saw God. All of the stories pointed to the idea that man could no see God and survive. Joseph Smith made note of this as well when he suggested that "that humans cannot see God with their “natural eyes” without being consumed. They could, however, witness his glory with “spiritual eyes” if they were changed or “quickened by the spirit of God.” Moses 1:11; D&C 67:11; Ether 12:19

Over time Martin Harris tried to use different language to express his encounter with the angel Moroni and the plates. He suggested that he saw them with “a spiritual eye,” but also with his physical senses. On one occasion he said "As sure as you are standing there and see me, just as sure did I see the angel with the golden plates in his hand." (Ole A. Jensen, quoted in J. M. Sjodahl, “The Credibility of the Witnesses,” Improvement Era, vol. 26, no. 11 (Sept. 1923), 975. Ole A. Jensen interviewed Harris in 1875.)

In 1870, at the age of 87, Harris accepted an invitation to live in Utah Territory, where he was rebaptized into The Church of Jesus Christ of Latter-day Saints (LDS Church) and spent his remaining years with relatives in Cache County. In his last years, Harris continued to bear fervent testimony to the authenticity of the plates, but a contemporary critic of the church has noted that Harris rejected some important Mormon doctrines and that his sympathy for the LDS Church was tenuous.[46] In a letter of 1870, Harris swore, "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."

From David Whitmer we have the description of his experience detailed as: “Of course we were in the spirit when we had the view, for no man can behold the face of an angel, except in a spiritual view, but we were in the body also, and everything was as natural to us, as it is at any time.” (“Letter of David Whitmer to Anthony Metcalf, March 1887,” in David Whitmer Interviews: A Restoration Witness, Lyndon W. Cook, ed. (Orem, Utah: Grandin Books, 1991): 246–7.)

The official church magazine Improvement Era published a statement by Jacob F. Gates, son of early Mormon leader Jacob Gates, who had died twenty years prior. According to the recollection by his son, the elder Gates had visited Cowdery in 1849 and inquired about his witness testimony concerning the Book of Mormon. Cowdery reportedly reaffirmed his witness: "Jacob, I want you to remember what I say to you. I am a dying man, and what would it profit me to tell you a lie? I know," said he, "that this Book of Mormon was translated by the gift and power of God. My eyes saw, my ears heard, and my understanding was touched, and I know that whereof I testified is true. It was no dream, no vain imagination of the mind—it was real". (Scott H. Faulring, The Return of Oliver Cowdery, Maxwell Institute; Gates, Jacob F. (March 1912). "Testimony of Jacob Gates". Improvement Era 15. p. 92.)

Oliver Cowdery and Martin Harris later returned to the church, David Whitmer did not. However; each affirmed until the day of their death to what they had acknowledged in their individual testimonies of what they witnessed regarding the plates and the Angel Moroni. You cannot really get more compelling evidence than that as each had their chance to say it was a hoax, that it was not true. They even were opposed to Jospeh Smith at times; they turned on him so to speak, but through it all they did not deny their sworn testimonies.