There has been much confusion regarding Matthew 5:13:
You are the salt of the earth: but if the salt has lost its savor, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men.
Many have interpreted this reference by first interpreting the use of the word salt to mean “to season,” explaining that to “loose saltiness” renders salt unable to season. Likewise, some have said that salt is to be understood as meaning “to preserve,” and that salt that can no longer preserve is useless. Both of these interpretations miss the point by interpreting the word “salt” in modern terms rather than ancient Hebrew terms.
To complicate this matter, there is quite a bit of misunderstanding surrounding the ancient meaning of the Hebrew word for salt, melach. Brown defines the term as having derived from the similar word malach (to tear away), and for many reasons, this is quite reasonable. The two words are often confused in the Bible. But, the word most likely derives from the root lach, “to wet,” or “to moisten.” The word lach also means “to lick” from the concept of wetting the lips and it is from this word that melach (m-lach or “that which is licked”) derives. A salt lick is a salt deposit that animals regularly lick. Another meaning of the word lach is “vigor,” or “lifeblood,” and essential ingredient of vitality and life. This is the connection between salt and the phrase “salt of the earth.”
To the Hebrews (and in fact almost all ancient eastern societies), salt was a symbol of the lifeblood and a substitute for blood itself in ceremonies involving the binding of people in bonds of friendship—so-called hospitality bonds. This is when two people swear loyalty to one another in a ceremony, known as a blood oath, where the blood of each man is mingled (often ceremonially) together.
According to Dennis Trumble in The Blood Covenant: A Primitive Rite and Its Bearings on Scripture: a Blood Covenant was..
“An agreement between two contracting parties, originally sealed with blood; a bond, or a law; a permanent religious dispensation. The old, primitive way of concluding a covenant (Hebrew, “to cut a covenant”) was for the covenanters to cut into each other’s arm and suck the blood, the mixing of the blood rendering them “brothers of the covenant. Originally the covenant was a bond of life-fellowship, where the mingling of the blood was deemed essential. In the course of time, aversion to imbibing human blood eliminated the sucking of the blood, and the eating and drinking together became in itself the means of covenanting, while the act was solemnized by the invocation of the Deity in an oath, or by the presence of representative symbols of the Deity, such as seven animals, or seven stones or wells, indicative of the seven astral deities; whence Hebrew (“to be bound by the holy seven”) as an equivalent for ‘swearing’ in pre-Mosaic times” (Trumble 1893).
Thus, in time, salt became a symbol used during the fellowship meal to represent the lifeblood and an exchange of salt came to represent the mingling of blood and therefore became a symbol of an indissoluble bond of friendship.
When Yeshua told his disciples that they were the “salt of the earth,” he was not saying that they were the “seasoning” of the earth, or the “preservative” of the earth. He was saying, “you are the lifeblood (or life-giving force) of the earth, without which it would be good for nothing.”