A look at the cross-references for 2 Nephi 1:20 reveals many other Book of Mormon references wherein the promise is repeated that those who keep the Lord’s commandments will prosper in the land. This appears to have been one of those prophetic utterances that was preserved in the hearts and the writings of the people from generation to generation. It is a promise that is still in force for the promised land (present-day North and South America). Those who are obedient will prosper both spiritually and temporally in the land.