What does Jesus mean when he says that we are the salt of the earth?
In the ancient world salt was considered essential for maintaining life. The Roman author Pliny said, “Without salt human life cannot be sustained.” The book of Sirach (180 B.C.) has it that “The basic necessities of human life are water and fire and iron and salt and wheat flour and milk and honey, the blood of the grape and oil and clothing” (Sir. 39:26). In a certain Rabbinic writing, it is said, “The world cannot endure without salt.”
So valued was salt that in different cultures it was sometimes used as a form of money. No doubt you have heard the phrase, “So and so is not worth his salt.” The saying has its origin in workers being paid at least a portion of their wages in salt. If someone is not worth his salt, he is not worth what he is being paid. We have a reminder of this historical fact (salt as money) in our word “salary,” which comes from salarium, the Latin word for salt.
One of the most obvious uses of salt is for seasoning. This use has been around since the beginning of time. It was recognized in the sacrificial system of the OT. The Lord told Israel, “You shall season all your grain offerings with salt…with all your offerings you shall offer salt” (Lev. 2:13).
The seasoning properties of salt were recognized by Job. He asks, “Can that which is tasteless be eaten without salt?” (Job 6:6). The expected answer is “no”. Things that are tasteless or insipid are so unappetizing as to be uneatable.
The world is a tasteless, insipid place without the righteous to season it. And the righteous do season it with the holiness of their lives. Consider how Paul instructs the Colossians:
Let your speech always be gracious, seasoned with salt, so that your may know how you ought to answer each person. (Col. 4:6)
Gracious, prudent, circumspect speech is one way in which we season the world. It seems that our culture is becoming increasingly vulgar, increasingly coarse and rude and crude. One of the ways in which we distinguish ourselves as Christians is by how we speak. We don’t imitate the way the world speaks.
Not only in speech, but in all our behavior, in what we do (deeds of love and kindness) and in what we don’t do, we are to make the world a more tasteful place
Salt was not only used for seasoning, but also for preservation. Of course people in the ancient world didn’t have refrigeration or any means of canning food for long-term storage, but they did have salt; and this was used to preserve food, especially meat. A high concentration of salt inhibits the growth of bacteria and other microorganisms by drawing the water out their cells. It takes up to twenty percent salt to properly preserve meat, but preserved in this way it could be kept for a very long time. Salted meat was a common staple on sea voyages until relatively recent times.
How does this property of salt apply when Jesus says, “You are the salt of the earth”? It applies in two ways. First, the presence of a faithful remnant of godly people slows down the rate of moral decay in a culture. It is the Christian community that functions as the conscience of a nation; more than this, it is the Christian community that functions as the prophetic voice of God to the nation. Imagine what the United States would be like today if there were no Christians bearing witness by word and deed to the truth of God. We rightly lament the moral degeneration of our times; but how much worse would things be if there were no Christians here laboring in the cause of the gospel, raising godly families, laboring in the political realm, raising their voices for truth and virtue?
The preservative properties of salt apply to us in another way: it is on account of the righteous that the world is spared the judgment it deserves at the time it deserves it (Gen. 18:22-32; Matt. 23:22-23).
It is for the sake of the righteous within a culture that God spares the culture the judgment it deserves at the time it deserves it. Sometimes the judgment is averted altogether. Sometimes it is merely delayed. Sometimes the judgment comes, but is mitigated. He does this as a favor to his people. He does it for their sake. It is one of his covenant mercies to them that the culture in which they live is spared judgment. The presence of a faithful remnant of godly people preserves a culture from the wrath of God.