Some of those greater things are things we already take for granted: an understanding of pre-mortal life, the council in heaven, the importance of temple work and genealogy, the three degrees of glory, and the full meaning of the term “exaltation.” But the Lord will give us more, just as soon as we’re ready. This includes things not yet revealed. As the Lord promised, in that day that they shall exercise faith in me, saith the Lord, even as the brother of Jared did…then will I manifest unto them the things which the brother of Jared saw, even to the unfolding unto them all my revelations (Ether 4:7).
Joseph Fielding Smith
"I would like to call your attention to one thing in the Book of Mormon. The Lord has promised us greater knowledge, greater understanding than we find in the Book of Mormon, when we are prepared to receive it. When the brother of Jared went upon the mount to have the Lord touch stones to give them light to light their way across the great ocean, the Lord revealed to him the history of this world from the beginning of it to the end. We do not have it.
“…Now the Lord has placed us on probation as members of the Church. He has given us the Book of Mormon, which is the lesser part, to build up our faith through our obedience to the counsels which it contains, and when we ourselves, members of the Church, are willing to keep the commandments as they have been given to us and show our faith as the Nephites did for a short period of time, then the Lord is ready to bring forth the other record and give it to us, but we are not ready now to receive it. Why? Because we have not lived up to the requirements in this probationary state in the reading of the record which had been given to us and in following its counsels.” (Conference Report, Oct. 1961, pp. 19-20)
Orson Pratt
"He that receives this record, and shall not condemn it because of imperfections that are in it, the same shall know of greater things than these. That is, they shall know of greater things than what are contained in the Book of Mormon. The Book of Mormon contains some wonderful things…Great things, historically, are revealed in this book…concerning prophecies that are yet to take place, and that have already taken place…
"It does not mean those who should read this record and not perform the things that are contained therein; the promise is not extended to them. ‘Whoso receiveth this record’…No man or woman that fails to comply with these things that I have named (faith, repentance, baptism, laying on of hands)--believes and receives the record; they may pretend to believe the record, they may say it appears to be a very good record, and it speaks as if it might be true; but unless they do receive it, by obeying its ordinances, and its institutions, and complying with the principles of the Gospel, they would not be entitled to the promise recorded in the words of my text, ’They shall know of greater things than these.’ (Journal of Discourses, 20:69)