sn Salt was used as seasoning or fertilizer (BDAG 41 s.v. ἅλας a), or as a preservative. If salt ceased to be useful, it was thrown away. With this illustration Jesus warned about a disciple who ceased to follow him.

sn The difficulty of this saying is understanding how salt could lose its flavor since its chemical properties cannot change. It is thus often assumed that Jesus was referring to chemically impure salt, perhaps a natural salt which, when exposed to the elements, had all the genuine salt leached out, leaving only the sediment or impurities behind. Others have suggested that the background of the saying is the use of salt blocks by Arab bakers to line the floor of their ovens; under the intense heat these blocks would eventually crystallize and undergo a change in chemical composition, finally being thrown out as unserviceable. A saying in the Talmud (b. Bekhorot 8b) attributed to R. Joshua ben Chananja (ca. a.d. 90), when asked the question “When salt loses its flavor, how can it be made salty again?” is said to have replied, “By salting it with the afterbirth of a mule.” He was then asked, “Then does the mule (being sterile) bear young?” to which he replied: “Can salt lose its flavor?” The point appears to be that both are impossible. The saying, while admittedly late, suggests that culturally the loss of flavor by salt was regarded as an impossibility. Genuine salt can never lose its flavor. In this case the saying by Jesus here may be similar to Matt 19:24, where it is likewise impossible for the camel to go through the eye of a sewing needle.