Sealed book of Mormon Ch.8

AND now, I, Moroni, have been
commanded by the Holy Spirit to explain
more, even in its fullness, the spirit world
which I have mentioned in the vision of the
brother of Jared. And the brother of Jared did
truly witness all these things, yea even all the
workings of the spirit world. Nevertheless,
these things were made known unto me long
before I used the interpreters to read the
words of the brother of Jared And these things were made known unto me
by the power of the Holy Spirit who is the God
of this spirit world, or in other words, its leader.
And my father also knew of the workings of this
spirit world of which I have made mention.
Nevertheless, he was commanded not to write
the things that he knew concerning it, and the
things that he knew were the same things that I
know, and also the same things that have been
written of by the brother of Jared.
And these things have been withheld from
the world because of the wickedness and
unbelief of the children of men. Behold, these
things have been reserved for the faithful who
have for a long time sought to understand the
workings of the spirit realm and the mysteries of
God that pertain unto it.
And many have believed that there existeth
a spirit realm that cannot be seen with mortal
eyes, nevertheless, they do not understand this
realm, nor do they understand its operations and
its government.