The saying is that salt adds flavor, therefore we are to shine our light in such a way that we could encourage the non-believers or the backsliders to know Christ. We are to spread the gospel, be genuine, be pure and our message should have flavor so it would reach others.

Jesus said 'let your light shine before men; that they may see your good works, and glorify your Father who is in Heaven.

Do not hide the word of God, instead spread it all aroung the world if you can.