The Disciples Are The Salt Of The Earth (5:13-14).
Jesus' first declaration about His disciples is that they are the salt of the earth. And this is then followed by a grave warning. For it is possible for (Palestinian) salt to lose its savour. And then what will the result be? It will be fit for nothing but to be thrown away to become the equivalent of the dust under men's feet.
Analysis of Matthew 5:13-14.
a “You are the salt of the earth (Matthew 5:13 a).
b But if the salt have lost its savour (literally ‘become foolish') (Matthew 5:13 b).
c With what will it be salted? (Matthew 5:13 c)
b It is from then on good for nothing (Matthew 5:14 a).
a But to be cast out and trodden under foot of men” (Matthew 5:14 b).
Note the parallels. In ‘a' it is the salt of the earth, influential and effective, while in the parallel it is useless and rejected, and fit only for men to treat with contempt. In ‘b' the salt loses its savour, and in the parallel it is thus good for nothing. And in ‘c' we have the central punch line. If this happens there is no way in which it can be restored.
Note also the advance in thought. First the idea itself, ‘you are the salt of the earth', then the warning, the salt can lose its savour, then the catastrophic realisation, if it does there is then no way for it to be re-salted, then the consequence, it is useless for anything, and then the result, it becomes something to be trodden under men's feet.
As we shall see, this combination of advance in thought alongside chiastic comparisons in parallel is a feature of the Sermon on the Mount, a sign of the genius that lay behind it.
In order to understand this illustration we have to know something about Palestinian ‘salt'. It was not pure salt. It was gathered from areas like those around the Dead Sea, and contained considerable impurities. When it was stored there was always the danger of dampness causing the actual salt (sodium chloride) to dissolve leaving behind a tasteless mass. The ‘salt' would then have lost its savour, and there would thus be no further use for it. Some, however, argue that it is the very impossibility of salt losing its savour that is the point behind the illustration. True disciples cannot lose their saltiness. Therefore those who do simply reveal that they were never salt at all. Either way the point is the same. Without saltiness they are worthless.