Mosiah 13

Abinadi teaches -

"...that salvation doth not come by the law alone; and were it not for the atonement, which God himself shall make for the sins and iniquities of his people, that they must unavoidably perish, notwithstanding the law of Moses."  (Mosiah 13:28)

The word "alone" suggests that obedience and works are still essential.  This has always been taught for -

"...did not Moses prophesy unto them concerning the coming of the Messiah, and that God should redeem his people? Yea, and even all the prophets who have prophesied ever since the world began—have they not spoken more or less concerning these things?"  (Mosiah 13:33)

Which truly suggest that many teachings have been removed from the Old Testament.