D&C 35:3-4, (BC 37) recorded Dec 1830, linked Rigdon to John the Baptist: “Behold, verily, verily, I say unto my servant Sidney, I have looked upon thee and thy works. I have heard thy prayers, and prepared thee for a great work. Thou art blessed, for thou shalt do great things. Behold thou wast sent forth, even as John – to prepare the way before me, and before Elijah, which should come, and thou knew it not. Thou didst baptise by water unto repentance, but they received not the Holy Ghost; but now I give unto thee a commandment, that thou shalt baptise by water, and they shall receive the Holy Ghost by the laying on of the hands, even as the apostles of old.” See: http://sidneyrigdon.com/wht/1891WhE5.htm
In 1838, Smith described the above visit of John the Baptist: “The messenger who visited us on this occasion and conferred this priesthood upon us said his name was John, the same that is called John the Baptist in the New Testament, and that he acted under the direction of Peter, James and John, who hold the Priesthood of Melchisedek, which Priesthood he said should in due time be conferred on us, and that I should be called the first elder and he the second. It was on the 15th day of 1829 that we were baptized, and ordained under the hand of the messenger.” JS-H 1:72
Said Darwin Atwater, a Patriarch in the Disciples Church at Mantua: “That he [Rigdon] knew before of the coming of The Book of Mormon is to me certain, from what he said the first of his visits to my father’s some years before [at about the close of January 1827]”. “He gave a wonderful description of the mounds and other antiquities found in some parts of America, and said they must have been made by the aborigines. He said there was a book to be published containing an account of those things. He spoke of these in his eloquent, enthusiastic style as being a thing most extraordinary.”
Dr. Storm Rosa, a well-known “botanic physician” of Ohio, said in, an 1841 letter to Rev. John Hall of Ashtabula: “In the early part of the year 1830 I was in company with Sidney Rigdon, and rode with him on horseback for a few miles…. He remarked to me that it was time for a new religion to spring up; that mankind were all right and ready for it.” See: http://sidneyrigdon.com/RigHist/RigHist2.htm
In a Jan 22, 1841 letter written to Walter Scott, Adamson Bentley said: “I know that Sidney Rigdon told me that there was a book coming out, the manuscript of which had been found engraved on gold plates, as much as two years before the Mormon Book made its appearance, or had been heard of by me.”
Thomas Clapp, a deacon in the church where Rigdon preached, confirmed Bentley’s statement: “Elder Adamson Bentley told me that as he was one day riding with Sidney Rigdon and conversing upon the Bible, Mr. Rigdon told him that another book of equal authority with the bible, as well authenticated and as ancient, which would give an account of the history of the Indian tribes on this continent, with many other things of great importance to the world, would soon be published. This was before Mormonism was ever heard of in Ohio, and when it appeared, the avidity with which Rigdon received it convinced him that if Rigdon was not the author of it he was at least acquainted with the whole matter some time before it was published to the world”.See: http://thedigitalvoice.com/enigma/wrw/1977DavD.htm#pg116b
The Reverend Samuel F. Whitney said: “I heard Sidney Rigdon preach in Squire Sawyers’ orchard in 1827 or ’28. He said how desirable it would be to know who built the forts and mounds about the country. Soon it would all be revealed. He undoubtedly referred to the “Book of Mormon” which was published in 1830.” http://www.sidneyrigdon.com/dbroadhu/CA/natruths.htm#010088-3b2
John Rudolph stated: “For two years before The Book of Mormon appeared Rigdon’s sermons were full of declarations and prophecies that the age of miracles would be restored, and more complete revelations, than those in the Bible, would be given. When The Book of Mormon appeared, all who heard him were satisfied that he referred to it.” (Cowdery et al., 2005, p. 313).