Christ describes his disciples as salt and light in this portion of the Sermon on the Mount.

Why salt? Preserving the world? Yes, but also because his people are called to be sacrifices sprinkled with salt, imparting to the world a pleasing taste to God. But salt also points to judgment:  where Christ is rejected, judgment comes.

Why light? We shine as bright stars in the darkness, even as the light of Christ shines in and through us. How? Not simply with words of teaching and testimony, as important and necessary as those are, but with the light of our good works, pleasing to God and for the good of our neighbors.

Christian, be salt and light.