Salt and light
Salt and light are images used by Jesus in the Sermon on the Mount, one of the main teachings of Jesus on morality and discipleship. These images in Matthew 5:13, 14, 15 and 16 immediately follow the Beatitudes and are often interpreted as referring to Jesus' expectations of his disciples.
The first verse of this passage introduces the phrase "salt of the earth":
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.
The second verse introduces "City upon a Hill":
You are the light of the world. A city located on a hill can't be hidden.
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. Even so, let your light shine before men; that they may see your good works, and glorify your Father who is in heaven.