Whereas in Mark 9.50 the disciples are told to have salt in themselves (Good News Translation “Have the salt of friendship among yourselves”), here they themselves are identified as the salt of the earth. Good News Translation transforms the metaphor You are the salt into a simile, “You are like salt.” In English, as in many other languages, the use of a simile (“X is like Y”) is clearer and more straightforward than a metaphor (“X is Y”).

As it stands, the genitive expression of the earth is difficult to understand because it leaves ambiguous the relation between salt and earth. New English Bible is an improvement (“You are salt to the world”), and Good News Translation has “… for all mankind.” Die Bibel im heutigen Deutsch entirely restructures (“What salt is for food, this is what you must be for the world”), and INCL has “You are like salt that is needed by this world.”

In many languages it will be necessary to specify in what way you are like salt. Some translations have felt the basis of the comparison is that in the same way salt gives flavor or savor to food, you must give flavor to the earth. But this is probably not what is meant here. It is more likely that you are to preserve or save the earth as salt preserves food. However, because of the variety of ways the expression can be interpreted, a large number of translations have preferred to say in the text “You are like salt for men,” and to discuss what it means in a footnote.

Of the earth, as we pointed out, means “for all people” or “for people everywhere.”

Has lost its taste is difficult to interpret. Salt that is used for food does not lose its taste or its saltness even if unused for a long period of time. This expression must therefore refer to the salt being diluted or somehow mixed with other substances so that it becomes ineffective. The root meaning of the verb is “make foolish” or “show to be foolish” (1 Cor 1.20), and in the passive, “become foolish” (Rom 1.22). Only in this verse and in Luke 14.34 do the lexicons give the meaning for the passive as “become tasteless.”

Scholars have suggested many possible explanations. One is that Jesus is referring to salt being mixed with other substances so that it is no longer effective. Another is that the salt retrieved from the Dead Sea contains other substances, and that if the salt is washed out and lost, only those worthless substances are left. Anchor Bible has “If the salt is of low grade,” and the authors in this way reflect their interpretation of the verb “become foolish” as referring to the salt becoming “insipid” by being mixed and thus weakened. Others suggest that a play on words was involved, in which the Hebrew word for “be foolish” resembles the Aramaic word for “seasoned, salty.” Another suggestion is that salt has been a symbol of wisdom, and that Jesus is warning his disciples not to become “foolish,” as indicated by the use of the Greek verb. Another possibility, of course, is that Jesus knew perfectly well that salt does not change, but that he simply used this unreal and surprising figure of speech in order to teach a lesson more effectively.

We must not assume that Jesus and his disciples knew nothing of the properties of salt. Instead, it is important to recognize the function of this saying of Jesus. First, it is better to regard the figure of salt as referring to preservation of food rather than to improving the taste, although both may be involved. Although Jerusalem Bible follows Revised Standard Version with “become tasteless,” most of the modern translations settle for the meaning “loses its strength” (Good News Translation, Die Bibel im heutigen Deutsch, An American Translation, Luther 1984). Second, he is saying that the disciples are the people who have the spiritual knowledge, wisdom, and way of life by which to preserve this world in a proper condition, and it is not the religious leaders or government officials who can do it. Third, he is warning his followers against a useless discipleship, one that is weak or diluted so as to become ineffective.

Because salt is known wherever Bible translations are prepared, there is no difficulty preparing a translation that preserves salt as a figure of speech. However, the translator should take care that the structure of the sentence will not cause undue difficulty for the practical application of the figure in the life of a Christian. Few translations choose the interpretation “be foolish” for lost its taste. More common are those who say “no longer tastes like salt,” “no longer does what salt should do,” or “if the salt becomes so impure that it is no longer really salt.” But “loses its strength” will be the most common.

The sentence continues by asking how shall its saltness be restored? The translation will depend on how “lost its taste” was translated, since it should be similar. Following the above examples, the clause can be “how can it be made to taste like salt again?” “how can it once more do what salt should do (or, once more act like salt)?” “how can it become salt again?” or “how can it regain its strength?”

It is no longer good for anything (Good News Translation “It has become worthless”) is more literally “It no longer has strength for anything.” Die Bibel im heutigen Deutsch has “One can no longer use it for anything.” Other options are “People have no further use for it,” “It is no longer good for anything,” or “You can do nothing with it,” as in Barclay.

Thrown out may have to be “thrown outside” or “thrown out of doors.”

Trodden (Good News Translation “trample”) is also used in Matthew 7.6 and Luke 8.5 with the same meaning. Elsewhere in the New Testament it is found only in Luke 12.1 and Hebrews 10.29. Trodden under foot does not mean people will deliberately walk on it or somehow try to stamp it into the ground. The idea is it will be out on the ground where people walk, perhaps even on a road.

Taking these things into account, the sentence can be translated “It is no longer good for anything, so it will just be thrown outdoors where it will be walked on” or “You can do nothing with it except throw it out, and there it will get walked on (or, people will walk on it).”

Quoted with permission from Newman, Barclay M. and Stine, Philip C. A Handbook on the Gospel of Matthew. (UBS Handbook Series). New York: UBS, 1988. For this and other handbooks for translators see here .