13Ye 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.
"The 'it' refers to the "World", not to the salt. The salt does not need to be salted — common sense. The world will be thrown out without the saving power of the salt, and salt represent a covenant.
14Ye are the light of
the world. A city that is set on an hill cannot be hid. 15Neither 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. 16Let your light so
shine before men, that they may see your good works, and glorify your Father
which is in heaven.
How do we get this light? Through our own efforts? Not at all:
"Then spake Jesus again
unto them, saying, I am the light of the world: he that followeth me shall not
walk in darkness, but shall have the light of life." (John 8: 12)
And
"This then is the message which we have heard of him, and declare unto you, that
God is light, and in him is no darkness at all." (1 John 1: 5)
The Sermon on the Mount teaches people what they will become in Christ, but these things are not fulfilled in our lives through our efforts, but by His Finished Work at the Cross.