Oliver Cowdery accidentally omitted the word first while copying from 𝓞 to 𝓟, probably because of the high frequency of the phrase “land of their inheritance” (see the discussion under 1 Nephi 10:3). Yet the phrase “the land(s) of X’s first inheritance” occurs five other times in the text; there is also one occurrence of “the place of X’s first inheritance” (in Alma 22:28). In each instance, the reference is to a people that first inherited a land but were later displaced. In five cases the reference is to the land of Nephi, which the Nephites abandoned to the Lamanites during the times of the first king Mosiah (as recorded in Omni 1:12). The people of Zeniff were the first Nephites to return to the land of Nephi:
We have similar references to the land of Nephi as a land or place of first inheritance in Mosiah 10:13, Alma 22:28, Alma 54:12, and Alma 54:13.
The sixth case describes the result of a war between two Jaredite kings, Noah and Shule:
In 1 Nephi 22:12, the phrase “lands of their first inheritance” refers to the return of the house of Israel to their original land of inheritance in the land of Palestine.
Summary: Restore the modifier first in 1 Nephi 22:12, the reading of the original manuscript (“the lands of their first inheritance”); such usage is consistent with other references to peoples being restored to their original lands.