Jesus said to his disciples:

13 “You are the salt of the earth, but if the salt has lost its flavor, with what will it be salted? It is then good for nothing, but to be cast out and trodden under the feet of men. 14 You are the light of the world. A city located on a hill can’t be hidden. 15 Neither do you light a lamp, and put it under a measuring basket, but on a stand; and it shines to all who are in the house. 16 Even so, let your light shine before men; that they may see your good works, and glorify your Father who is in heaven."

Matthew 5:13-16 - World English Bible

The parables of salt and light lie at the heels of the Beatitudes. Jesus preached his blessings as a definition for the disciple, one who was counter-cultural (the first three Beatitudes), virtuous, (next four) and persecuted (final two). The stress these standards had on a possible convert or neophyte could be daunting.

Yet, the Christian could not shrink away. He was like the salt pillar of a clan, used for flavor and as a preservative for meats and fish. These pillars were never really pure, but contained dirt. When the clan could no longer retrieve any meaning amounts of salt from the pillar, they would throw it out onto the road, where the dirt-salt mixture actually hardened the by-way. So, the Christian had to maintain some sense of "purity" (devotion) in spite of the world's pollution, otherwise they would be "trampled under foot by men" (held in contempt).

The true disciple showed his faith by word and example, like a light in the darkness. He could not hide his actions; indeed, his deeds should point others towards faith, for the reputation of the Father of the Christ depended upon the reputation of the Christian.

How are you salt and light to those around you?