"Ye are the salt of the earth: but if the salt have lost his savour, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men. Ye are the light of the world. A city that is set on an hill cannot be hid. Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light unto all that are in the house. Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven." (Matthew 5: 13-16)
These are some very interesting verses. We'll often hear Christians say how we are called to be the light of the Earth, or the salt of the Earth. The problem is that if the verses are interpreted in that light (no pun intended), then it becomes a future event. After salvation in the right way, a Christian is then the light and the salt.
But that's not really what the verses are saying. Jesus says these things very early in Matthew, and before the crucifixion. What's more, he's speaking to his disciples and a crowd. The crowd which later marvels at Jesus's teachings when he was done speaking. And Jesus is speaking in the present tense. It can easily be interpreted that Jesus is saying what everyone is right now -- the light of the Earth, or the salt - and that no one should hide it. The crowd falling into those categories has nothing to do with their spiritual status. Rather, Jesus is almost trying to wake everyone up to what s/he already is. The crowd must simply embrace it, and live that life. They must let that light shine forth before men, so everyone can glorify their Father in heaven (which leads to another point. The crowd was already the children of God, even though they hadn't said/believed the right things).
Now, it can be argued that these words only applied to the disciples. The problem then is if that's the case, then the concept of sinning through lust or hatred can only apply to the disciples, too. And the crowd is excluded from that judgement. But Jesus was speaking to the crowd. So wasn't everyone in that crowd already the light of the world? And simply blinded to the fact?