Sealed book of Mormon Ch.12

AND now, I, Moroni, have written many of
the words of the brother of Jared concerning
the Holy Endowment that the Lord gave
unto Adam and Eve and commanded them
to present to their children so that they
might have some measure of knowledge
regarding the plan of salvation that the
Father gave unto them in His kingdom, but
which the children of men cannot remember
in mortality. And this same endowment was given unto
Lehi when he entered the land of promise. And
Lehi taught these things unto his son Nephi,
who caused temples to be built in the land of
Lehi-Nephi for the instruction and edification of
the Nephites.
And I have the large plates of Nephi in
which are written these things. Nevertheless,
the Lord commanded my father Mormon not to
include them on the plates upon which he hath
abridged the record of Nephi.
And in the day of my father, and also in my
own day, this holy endowment hath been
corrupted by the church and its leaders. But this
church and these leaders have all been destroyed
by the Lamanites. And they have also destroyed
the temples and the places that were dedicated to
teach these things unto the people.
However, it would not have mattered to
the Lord if his people received the endowment
that was being taught by the church in my day,
because it was changed and corrupted,
evensomuch that it did not have the signs or
the penalties of which the brother of Jared
hath written.
And it confused the people who received it
more than it lifted them up and taught them the
mysteries of God.