Ye are the salt of the earth - Salt renders food pleasant and palatable, and preserves from putrefaction. So Christians, by their lives and instructions, are to keep the world from entire moral corruption. By bringing down the blessing of God in answer to their prayers, and by their influence and example, they save the world from universal vice and crime.
Salt have lost its savour - That is, if it has become tasteless, or has lost its preserving properties. The salt used in this country is a chemical compound - chloride of sodium - and if the saltness were lost, or it were to lose its savor, there would be nothing remaining. It enters into the very nature of the substance. In eastern countries, however, the salt used was impure, or mingled with vegetable or earthy substances, so that it might lose the whole of its saltness, and a considerable quantity of earthy matter remain. This was good for nothing, except that it was used to place in paths, or walks, as we use gravel. This kind of salt is common still in that country. It is found in the earth in veins or layers, and when exposed to the sun and rain, loses its saltness entirely. Maundrell says, “I broke a piece of it, of which that part that was exposed to the rain, sun, and air, though it had the sparks and particles of salt, yet it had perfectly lost its savor. The inner part, which was connected to the rock, retained its savor, as I found by proof. So Dr. Thomson (The Land and the Book, vol. ii. pp. 43, 44) says, “I have often seen just such salt, and the identical disposition of it that our Lord has mentioned. A merchant of Sidon having farmed of the government the revenue from the importation of salt, brought over an immense quantity from the marshes of Cyprus - enough, in fact, to supply the whole province for at least 20 years. This he had transferred to the mountains, to cheat the government out of some small percentage. Sixty-five houses in June - Lady Stanhope’s village were rented and filled with salt. These houses have merely earthen floors, and the salt next the ground, in a few years, entirely spoiled. I saw large quantities of it literally thrown into the street, to be trodden underfoot by people and beasts. It was ‘good for nothing.’
“It should be stated in this connection that the salt used in this country is not manufactured by boiling clean salt water, nor quarried from mines, but is obtained from marshes along the seashore, as in Cyprus, or from salt lakes in the interior, which dry up in summer, as the one in the desert north of Palmyra, and the great lake of Jebbul, southeast of Aleppo.
“Maundrell, who visited the lake at Jebbul, tells us that he found salt there which had entirely ‘lost its savor,’ and the same abounds among the debris at Usdum, and in other localities of rocksalt at the south end of the Dead Sea. Indeed, it is a well-known fact that the salt of this country, when in contact with the ground, or exposed to rain and sun, does become insipid and useless. From the manner in which it is gathered, much earth and other impurities are necessarily collected with it. Not a little of it is so impure that it cannot be used at all, and such salt soon effloresces and turns to dust - not to fruitful soil, however. It is not only good for nothing itself, but it actually destroys all fertility wherever it is thrown; and this is the reason why it is cast into the street. There is a sort of verbal verisimilitude in the manner in which our Lord alludes to the act: ‘it is cast out’ and ‘trodden under foot;’ so troublesome is this corrupted salt, that it is carefully swept up, carried forth, and thrown into the street. There is no place about the house, yard, or garden where it can be tolerated. No man will allow it to be thrown on to his field, and the only place for it is the street, and there it is cast to be trodden underfoot of men.”