"Blessed are you when people insult you, persecute you and falsely say all kinds of evil against you because of me. Rejoice and be glad, because great is your reward in heaven, for in the same way they persecuted the prophets who were before you.
You are the salt of the earth. But if the salt loses its saltiness, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled underfoot.
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 bowl. Instead they put it on its stand, and it gives light to everyone in the house. In the same way, let your light shine before others, that they may see your good deeds and glorify your Father in heaven."
Jesus Christ, Matthew 5v11-16
"What is most salty and bright in this insipid and dark world is the almost incomprehensible joy of Jesus' followers in the midst of persecution and the hardships of life. It is a joy that is meek and merciful and pure and peaceable, but these things alone do not awaken people to the glory of God. In order to waken people to consider God as an explanation for our good works there generally must be an obstacle of suffering that would ordinarily cause them to be angry or despairing, but does not have that effect on us. Rather they see us "rejoice" in hardship. They see that this hardship does not make us self-centred and self-pitying and mean-spirited. Instead they see our joy and wonder what we are hoping in when ordinary props for hope have been knocked away. The answer, Jesus says, is that we have great reward in heaven. That is, Jesus has become a treasure for us that is more precious than what the world offers. Therefore, when persecution or calamity take natural pleasures away, we still have Jesus, and we still have joy."
John Piper, What Jesus Demands From The World, IVP