From Matt. 5:13 - immediately following the section known as the Beatitudes (on the Mount of olives) Jesus turns to his disciples and tells them this -- You are the salt of the earth but if the salt has become tasteless how will it be made salty again? It is good for nothing any more except to be thrown out and trampled underfoot by men. You are the light of the world. A city set on a hill cannot be hidden.