Ye are the salt of the earth. — The words are spoken to the disciples in their ideal character, as the germ of a new Israel, called to a prophetic work, preserving the earth from moral putrescence and decay. The general reference to this antiseptic action of salt is (as in Colossians 4:6, and possibly in the symbolic act of Elisha, 2 Kings 2:21) enough to give an adequate meaning to the words, but the special reference to the sacrificial use of salt in Mark 9:49 (see Note there) makes it probable enough that there was some allusion to that thought also here.
If the salt have lost his savour. — The salt commonly used by the Jews of old, as now, came from Jebel-Usdum, on the shores of the Dead Sea, and was known as the Salt of Sodom. Maundrell, the Eastern traveller (circ. A.D. 1690), reports that he found lumps of rock-salt there which had become partially flavourless, but I am not aware that this has been confirmed by recent travellers. Common salt, as is well known, will melt if exposed to moisture, but does not lose its saltness. The question is more curious than important, and does not affect the ideal case represented in our Lord’s words.
Wherewith shall it be salted? — The words imply a relative if not an absolute impossibility. If gifts, graces, blessings, a high calling, and a high work fail, what remains? The parable finds its interpretation in Hebrews 6:1-6.
To be trodden under foot of men. — The Talmud shows (Schottgen in loc.) that the salt which had become unfit for sacrificial use in the store-house was sprinkled in wet weather upon the slopes and steps of the temple to prevent the feet of the priests from slipping, and we may accordingly see in our Lord’s words a possible reference to this practice.