Nobody likes to hear the phrase, "I told you so!" But those who reject the Book of Mormon will be shown their folly at the last day. In essence, they will hear "I told you so" from the Savior who said, ye shall know that it is I that speaketh, at the last day (Ether 4:10). They will hear "I told you so" from the three witnesses whose declaration shall stand as a testimony against the world at the last day. They will hear "I told you so" from every member of the Godhead, for the Father, and the Son, and the Holy Ghost [will] bear record. Finally, they will hear "I told you so" from Moroni who warned, ye shall know that I have authority when ye shall see me, and we shall stand before God at the last day (v. 6). Who else will be there to condemn the unbeliever? Will it be Joseph Smith? Will it be the missionary who first delivered the book? Will it be a teacher, a bishop, or a friend? Finally, it will be the unbeliever himself; convinced of his own error, he will be condemned by his own conscience.
Bruce R. McConkie
"Though men may reject the teachings of the apostles and prophets concerning Jesus Christ and his gospel, yet those very teachings shall rise to condemn the unbelievers in the day of judgment. That is, the words of the apostles and prophets shall stand as a testimony against unbelievers at the judgment bar of Christ. (2 Ne. 33:10-14; Moro. 10:27-29, 34.)" (Doctrinal New Testament Commentary, 1:330)