D&C 31

Paul taught -

"But wilt thou know, O vain man, that faith without works is dead?" (New Testament James 2:20)

And referring to Abraham -

"Seest thou how faith wrought with his works, and by works was faith made perfect?"  (New Testament James 2:22)

Throughout the Book of Mormon, we are taught that we are not saved by the Law of Moses, but through Christ and his atonement.  In a sense, we are saved by grace not works.  But nonetheless, where many miss the boat is that works is an essential condition to receive grace and forgiveness of our sins.  The Lord said to Thomas B. Marsh -

"...begin to preach from this time forth, yea, to reap in the field which is white already to be burned.
5 Therefore, thrust in your sickle with all your soul, and your sins are forgiven you..."  (Doctrine and Covenants Section 31:4 - 5)

Works is that which provides sufficient faith that allows the atonement to become effective in our lives.