Matthew 5:13-16

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 by men.  You are the light of the world.  A city on a hill cannot be hidden.  Neither do people light a lamp and put in 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 men, that they may see your good deeds and praise your Father in heaven.

These two metaphors, used to describe Jesus' disciples, are meant for making one basic point, or their meanings are atleast connected to each other.  The first one Jesus uses, the salt metaphor, is meant to make the point that the disciples must flavor the world in a good way.  The disciples must be virtuous.  There must be wisdom, passion, strength, humility, love and compassion, as well as many other good things.  In other words, the character of the disciples must reflect the character of Jesus.  If it is not so, then they will be "thrown out and trampled by men".  Its almost literal.  If a person does not have this solid character, or saltiness, then no one is going to respect them.  And since a disciple of Christ is a representative of Christ, we must represent well.

The second metaphor is saying almost the same thing.  The disciples are light, and as we all know, light is a good thing.  Without light we would all be wandering around completely lost and confused.  In fact, life would be impossible.  So Jesus commands his disciples to share their light, to do good deeds.  Why?  So that the world would see them and praise the Father in heaven.  A disciple of Christ should not be shy about being righteous.  We should not hide our good traits, but let them show clearly in good actions.

Now a person may wonder: doesn't this contradict some of Jesus' other teachings, like say Matthew 6:1 (also the sermon on the mount)?  It may seem at first like a contradiction, but its actually a paradox.  With all paradoxes in the Bible we must dig deeper and find the reason for it.  With these two teachings its all about motive.  The reason for letting people see your righteous deeds, and thus your righteous character, is so that God would be glorified.  But Jesus warns us not to do our 'acts of righteousness' before men, to be seen by men.  The reason is because there are some that seek glory for themselves.  The Pharisees and teachers of the law were much like this, and there's a good chance Jesus was thinking of them when he said those words.  Whenever we do any good deed, whether people know about it or not, we must do it to please God and bring God glory.  It is not something we should do so that others would say 'Here is a good man'.  Its something we should do so that others would say 'Praise God!'