3 Nephi 18

After the Savior had introduced the sacrament to those in the Americas, He turned to His disciples (leaders) and said to them -

"Blessed are ye for this thing which ye have done, for this is fulfilling my commandments, and this doth witness unto the Father that ye are willing to do that which I have commanded you." (Book of Mormon 3 Nephi 18:10)

And then He follows with this warning -

"...And if ye shall always do these things blessed are ye, for ye are built upon my rock.
13 But whoso among you shall do more or less than these are not built upon my rock, but are built upon a sandy foundation; and when the rain descends, and the floods come, and the winds blow, and beat upon them, they shall fall, and the gates of hell are ready open to receive them." (Book of Mormon 3 Nephi 18:12 - 13)

I sense the importance of His leaders doing exactly as He commands for -

"...whether by mine own voice or by the voice of my servants, it is the same." (Doctrine and Covenants Section 1:38)

For He has warned His leaders -

"...the day cometh that they who will not hear the voice of the Lord, neither the voice of his servants, neither give heed to the words of the prophets and apostles, shall be cut off from among the people;
15 For they have strayed from mine ordinances, and have broken mine everlasting covenant;
16 They seek not the Lord to establish his righteousness, but every man walketh in his own way, and after the image of his own god, whose image is in the likeness of the world, and whose substance is that of an idol, which waxeth old and shall perish in Babylon, even Babylon the great, which shall fall." (Doctrine and Covenants Section 1:14 - 16)

The Lord has declared to His leaders -

"...notwithstanding those things which are written, it always has been given to the elders of my church from the beginning, and ever shall be, to conduct all meetings as they are directed and guided by the Holy Spirit." (Doctrine and Covenants Section 46:2)

Some suggest that there is the spirit of the law and also the letter of the law. I feel the spirit of the law must fall within the bounds of the letter of the law. Elder Neal A. Maxwell said -

“One of the ironies which is fostered, at times innocently, in the Church, is the feeling we have that the spirit of the law is superior to the letter of the law because for some reason it seems more permissive or less apt to offend others. The reverse is true. The spirit of the law is superior because it demands more of us than the letter of the law. The spirit of the law insists that we do more than merely comply superficially. It means, too, that we must give attention to the things that matter most and still not leave the others undone” (For the Power Is in Them, pp. 46–47).

Therefore -

"...ye must watch and pray always, lest ye be tempted by the devil, and ye be led away captive by him.
16 And as I have prayed among you even so shall ye pray in my church, among my people who do repent and are baptized in my name. Behold I am the light; I have set an example for you." (Book of Mormon 3 Nephi 18:15 - 16)

And He promises if we do -

"...blessed are ye if ye shall keep my commandments, which the Father hath commanded me that I should give unto you." (Book of Mormon 3 Nephi 18:14)