D&C 41

As the saints were told that the Lord was about to reveal His law, the Lord explained -

"...ye shall receive my law, that ye may know how to govern my church and have all things right before me."  (Doctrine and Covenants | Section 41:3)

And then He warns -

"He that receiveth my law and doeth it, the same is my disciple; and he that saith he receiveth it and doeth it not, the same is not my disciple, and shall be cast out from among you;
6 For it is not meet that the things which belong to the children of the kingdom should be given to them that are not worthy, or to dogs, or the pearls to be cast before swine."  (Doctrine and Covenants | Section 41:5 - 6)

The doctrine that is least understood by many people is "and doeth it".  We must learn to do His work and His will.