In his debate with the wicked priests of King Noah, the prophet Abinadi is recorded as having said:
And now ye have said that salvation cometh by the law of Moses. I say unto you that it is expedient that ye should keep the law of Moses as yet; but I say unto you, that the time shall come when it shall no more be expedient to keep the law of Moses. (Mosiah 13:27)
Here, Abinadi informs them that, as he (and they) were living during the Old Testament side of salvation history, they had to keep the Law of Moses; notwithstanding, keeping the Law of Moses is not salvific. Such helps shed light on the phrase "after all we can do" in 2 Nephi 25:23.
My friend and fellow LDS apologist, James Stutz, has written an excellent article on this topic, and one I am in agreement with:
