Exegesis:

kalon oun to halas ‘salt is good.’ oun is difficult to interpret as to its reference, and best left untranslated.

halas ‘salt,’ here probably referring to discipleship.

ean de kai to halas mōranthē ‘but if even the salt becomes tasteless.’

mōrainō in the passive ‘to become tasteless,’ ‘to lose strength/flavour.’

en tini artuthēsetai ‘with what can it (i.e. the salt) be seasoned?.’ artuō.

Translation:

Jesus concludes by referring to a general truth, leaving it to his hearers to draw the inference; this may make advisable the use of some such introductory expression as, ‘remember,’ ‘you all know.’

Salt is good; but if …, or, ‘even though salt is good, if….’

Has lost its taste, or, ‘no longer has its taste/flavour,’ ‘has become insipid’ (Bahasa Indonesia, using the opposite of ‘salt-ish’), “loses its strength” (An American Translation, similarly Tae’); in Sranan Tongo the idiom is, ‘becomes dead.’

How shall its saltness be restored?, or, ‘how will it be given flavour again?,’ ‘how can it be made salt/salt-ish again?,’ ‘what will you take to awaken/raise it again?’ (Sranan Tongo); or as a statement, “there is no way to make it good again” (Good News Translation). If an active construction has to be used, the subject can best be ‘people,’ or, ‘we’ (inclusive).

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.