... you speak of "swapping wives," and state that you have it from one who knows. Now let me say to you that I never heard of it till I read it in your book. Your informant must have been deceived or willfully lied to you. Joseph Smith never proposed anything of the kind to me or to my wife; both he and Emma knew our sentiments in relation to spiritual wives and polygamy; knew that we were immoveably [sic] opposed to polygamy in any and every form; that we were so subsequent events proved. The story may have grown out of the fact that Joseph offered to furnish his wife, Emma, with a substitute for him, by way of compensation for his neglect of her, on condition that she would forever stop her opposition to polygamy and permit him to enjoy his young wives in peace and keep some of them in her house and to be well treated, etc.
["The Mormons in Nauvoo: Three Letters from William Law on Mormonism" as published in the Daily Tribune (Salt Lake Tribune) Tuesday, July 3, 1887 provided by Dr. Wly]