You are the salt of the earth. But if the salt loses its savor, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled by men.

You are the light of the world. A city on a hill cannot be hidden. Neither do people light a lamp and put it under a basket. Instead, they set it on a stand, and it gives light to everyone in the house. In the same way, let your light shine before men, that they may see your good deeds and glorify your Father in heaven.

Matthew 5:13-16