Precepts of God and precepts of men

The word, 'precept' does not appear in the Book of Mormon very often. In fact, all occurrences are found in 2 Nephi 27 and 28. In these chapters, Nephi is paraphrasing Isaiah 28:13

But the word of the Lord was unto them precept upon precept

and quoting Isaiah 29:13

their fear toward me is taught by the precept of men

From Isaiah, Nephi gets the contrasting idea of precepts of God and precepts of men and expands on this in his comments in 2 Nephi 28. His teachings lay out this contrast. First he explains what those precepts of men are

5 And they deny the power of God, the Holy One of Israel; and they say unto the people: Hearken unto us, and hear ye our precept; for behold there is no God today, for the Lord and the Redeemer hath done his work, and he hath given his power unto men;

6 Behold, hearken ye unto my precept; if they shall say there is a miracle wrought by the hand of the Lord, believe it not; for this day he is not a God of miracles; he hath done his work.

The precepts of men is that there is no God or he has done his work, therefore there are no miracles. This kind of language is repeated in Mormon and Moroni's writing, like Mormon 9 and Moroni 7. In 2 Nephi 28:26 and 31, Nephi goes on to explain

Yea, wo be unto him that hearkeneth unto the precepts of men, and denieth the power of God, and the gift of the Holy Ghost!

Cursed is he that putteth his trust in man, or maketh flesh his arm, or shall hearken unto the precepts of men, save their precepts shall be given by the power of the Holy Ghost. 

We see the same theme. Hearkening unto the precepts of men means denying God, his power, gifts and miracles. Compare with Moroni 7:35-36

has the day of miracles ceased? Or have angels ceased to appear unto the children of men? Or has he withheld the power of the Holy Ghost from them?

and Mormon 9:7

And again I speak unto you who deny the revelations of God, and say that they are done away, that there are no revelations, nor prophecies, nor gifts, nor healing, nor speaking with tongues, and the interpretation of tongues

and Moroni 10:7

And ye may know that he is, by the power of the Holy Ghost; wherefore I would exhort you that ye deny not the power of God

The precepts of men lead us to do what Mormon and Moroni warn against; deny the things that God has given us for our benefit and progression. Nephi says "wo unto him" and "cursed is he" that hearkens unto these precepts. On the other hand

thus saith the Lord God:...blessed are those who hearken unto my precepts (2 Nephi 28:30)

Hearkening unto the precepts of God or the precepts of men is also an example of "The Two Ways", that we encounter all over the Book of Mormon. 

A major theme in the chapters 27-29 is the Book of Mormon that should come forth. 2 Nephi 28:30 that I just quoted, is clearly linked up to this theme. That is, an important part of the precepts that God wants to give his children is the Book of Mormon. The Book of Mormon testifies of Christ and his gifts and miracles. It counters the precepts of men. How fitting that the last authors of the Book of Mormon, Mormon and Moroni warn us against the unbelief that comes from the precepts of men in the latter days and urge us instead to receive the words that they wrote because they are the "words of Christ" (Moroni 10:26-27).

As Joseph Smith said:

“I told the brethren that the Book of Mormon was the most correct of any book on earth, and the keystone of our religion, and a man would get nearer to God by abiding by its precepts, than by any other book.”