I find it interesting that Jesus never told the Jewish nation they to be salt and light. He said, "You are the salt of the earth" (Matt 5:13). "You are the light of the world" (Matt 5:14).

The question then is not if we are being salt and light but what kind of salt and light we are being. Is your salt tastless or is it packed with zest? Is your light being carefully hidden or does it shine like a city on a hill a midnight? John Stott wrote,

The whole church is called—and every member of it—as much to involvement in the world as to separation from it, as much to "worldliness" as to "holiness." Not to a worldliness which is unholy, nor to a holiness which is unworldly, but to "holy worldliness," a true separation to God which is lived out in the world—the world which he made and sent his Son to redeem.