Alma 22

Mormon lays out he process that Aaron taught king Laman -

"...Aaron did expound unto him the scriptures from the creation of Adam, laying the fall of man before him, and their carnal state and also the plan of redemption, which was prepared from the foundation of the world, through Christ, for all whosoever would believe on his name.
14 And since man had fallen he could not merit anything of himself; but the sufferings and death of Christ atone for their sins, through faith and repentance, and so forth; and that he breaketh the bands of death, that the grave shall have no victory, and that the sting of death should be swallowed up in the hopes of glory; and Aaron did expound all these things unto the king."  (Book of Mormon | Alma 22:13 - 14)

Aaron like so many other Book of Mormon prophets explained -

"...since man had fallen he could not merit anything of himself; but the sufferings and death of Christ atone for their sins, through faith and repentance, and so forth..."  (Book of Mormon | Alma 22:14)

That is the very essence of the plan of salvation.