Matthew 5:13 “You are the salt of the earth; but if salt has lost its taste, how can its saltiness be restored? It is no longer good for anything, but is thrown out and trampled underfoot.”
This particular passage in the Sermon on the Mount gets a lot of airplay, much more than that crazy “love your enemies” stuff. Salt serves two purposes that I know of, to add flavor to food and to preserve food. On the first count the church is guilty of losing its saltiness. We no longer create culture, we copy it. The God we represent is apparently an imitator not a Creator. For all the Christian versions of music, movies, books and board games, none of it is original. What would it look like if instead of adding a subculture consisting of substitutes for American culture, we created a real alternative culture. That would be the kind of spice others would notice.
The second purpose of salt, preservation, seems more vague. To make an interpretive leap, preserving the earth is exactly what humanity was commanded to do in the creation accounts. I don’t know that Jesus was specifically thinking about conservation, environmentalism or creation care (whichever you prefer), but it fits within Jesus’ teaching as well as the biblical narrative. So, I think I’m on safe ground here.
The point of the passage seems to be that Jesus’ followers have a message and a purpose, a flavor they add to the world. If they lose this flavor and no longer add anything, but only become imitators, they have become worthless, no longer serving their intended purpose. Thus the harsh words about being thrown out and trampled. We can find uses for old bananas (banana bread) and other foods past their prime, but salt and spices that have no flavor have to be tossed out.