If I’ve heard it once, I’ve heard it 100x: Christians are to be salt and light in this world. What that means is that we are to be marked by social justice or social activism or an influential presence in society. John R.W. Stott over and over used “salt and light” for the complement to evangelism, with “light” means evangelism and “salt” means social activism. This is at the least the “history of influence” of this set of images in Matthew 5:13-16, which I discuss in The Sermon on the Mount. And my friend Joel Willitts was the first to bring a different view to my attention, which I investigated and then fleshed out.
Furthermore, it seems “salt” has become the occasion for all sorts of learned speculation leading to all sorts of rather confident assumptions about what “salt” means: flavor, preservation, purification, the salt of a sacrifice, etc.. In my commentary I ponder such discussions but wonder if you have considered this:
Why does Jesus change from “earth” to “world”? That is, You are the salt of the earth but you are the light of the world. Are these the same ideas with earth and world being synonyms? If he meant the same why not use the same term? Of course, one might say because of the Jewish love of parallelism… OK, but I’m not convinced that works here.
Knowledge of the Jewish context would make it fairly certain that when Jesus said “earth” he meant “land” (ha-aretz) and this immediately complicates the picture. Is Jesus saying you are the salt of the land, that is, the holy land? I think that is the natural reading of “earth” and not its common view that it means world.
And knowledge of the Jewish context makes the “light of the world” immediately recall to mind Israel’s task: they were to be a light to the nations (a near equivalent to “world”). Thus, Isaiah 51:4 and 60:3 come to mind, and Jesus too is connected with this very idea: when he moves into the Galilee he has become a light (Matthew 4:14-16 — only one chp earlier, readers).
So, it seems to me Jesus has mind two audiences: the holy land and the wider Roman world. They are salting the land and bringing light to the world.
How so? This is where fanciful speculation about the sort of influence one finds in salt or in light needs to be checked against the text. Jesus explicitly defines what light means: “good works.” That’s precisely what 5:16 says.
Put together: our calling, or the disciples calling, is to reveal the gloriousness of God in the land and in the world on the basis of good works.