Brent Farley notes that those who follow the path marked by the beatitudes are accounted as “salt” and “light”! (3 Nephi 12:13-16) Salt has a distinctive property (or savor) that enhances the flavor of foods. Its addition tends to bring out the best of that to which it is added. So would the saints become the enhancers of those who accept the gospel. The commission to do this had a warning, however. If the savor was lost, then “wherewith shall the earth be salted? The salt shall be thenceforth good for nothing, but to be cast out and to be trodden under foot of men” (3 Nephi 12:13) Salt does not lose its savor by age, but rather by mixture and contamination. Correspondingly, the gospel does not lose its savor by age, but rather when it is mixed with the philosophies of men and devils. Salt is also a preservative. The gospel was intended to be preserved in purity. Its effects were to preserve the saints in righteousness that they might attain their celestial destiny. How appropriate was the Lord’s analogy!
The Saints, the “salt of the earth,” were also to be lights to which people in a darkened world could seek… . The symbolism of light and salt were appropriately placed together in the sacred text. Old Testament sacrificial rituals used salt as a token of gospel covenants. (See Leviticus 2:13 and Numbers 18:19) The Lord explained to Joseph Smith: “I have sent mine everlasting covenant into the world, to be a light to the world, and to be a standard for my people, and for the gentiles to seek to it, and to be a messenger before my face to prepare the way before me.” (D&C 45:9; emphasis added) Thus salt represents the gospel covenant, which is a light to the world. [S. Brent Farley, “The Appearance of Christ to the People of Nephi,” in Studies in Scripture: Book of Mormon, Part 2, pp. 154-155]