There are about 40 occurrences of the word, salt, in the Bible. Here are some of them:
Salt was part of the offerings to Yahweh: Leviticus 2:13 Every offering of your meal offering you shall season with salt. You shall not allow the salt of the covenant of your God to be lacking from your meal offering. With all your offerings you shall offer salt.
Salt was used to poison the fields of enemy nations: Judges 9:44 Abimelech and the companies that were with him rushed forward and stood in the entrance of the gate of the city; and the two companies rushed on all who were in the field and struck them. 45 Abimelech fought against the city all that day; and he took the city and killed the people in it. He beat down the city and sowed it with salt.
Deuteronomy 29:23 that all of its land is sulfur, salt, and burning, that it is not sown, doesn’t produce, nor does any grass grow in it, like the overthrow of Sodom, Gomorrah, Admah, and Zeboiim, which Yahweh overthrew in his anger, and in his wrath.
But salt, in at least one case, had the opposite effect, presumably because of a miracle: 2 Kings 2:19 The men of the city said to Elisha, “Behold, please, the situation of this city is pleasant, as my lord sees; but the water is bad, and the land is barren. 20 He said, “Bring me a new jar, and put salt in it.” Then they brought it to him. 21 He went out to the spring of the waters, and threw salt into it, and said, “Yahweh says, ‘I have healed these waters. There shall not be from there any more death or barren wasteland.’”
Offerings were supposed to be salted:
Leviticus 2:13 Every offering of your meal offering you shall season with salt. You shall not allow the salt of the covenant of your God to be lacking from your meal offering. With all your offerings you shall offer salt.
Numbers 18:19 All the wave offerings of the holy things which the children of Israel offer to Yahweh, I have given you and your sons and your daughters with you, as a portion forever. It is a covenant of salt forever before Yahweh to you and to your offspring with you.”
Salt was used in part of the ritual of establishing a covenant:
2 Chronicles 13:5 Ought you not to know that Yahweh, the God of Israel, gave the kingdom over Israel to David forever, even to him and to his sons by a covenant of salt? (I'm not sure whether salt was used in covenants between people, or just in covenants between God and people.)
Babies were salted at birth: Ezekiel 16:4 As for your birth, in the day you were born your navel was not cut. You weren’t washed in water to cleanse you. You weren’t salted at all, nor wrapped in blankets at all. (It may be that some of the significance of salt, as in putting it on babies, were prevalent just at the time related to that scripture. Or these practices may be widespread.
Here are some references from the New Testament: Matthew 5:13 “You are the salt of the earth, but if the salt has lost its flavor, with what will it be salted? It is then good for nothing, but to be cast out and trodden under the feet of men.
Luke 14:34 “Salt is good, but if the salt becomes flat and tasteless, with what do you season it?
Colossians 4:6 Let your speech always be with grace, seasoned with salt, that you may know how you ought to answer each one.
For the Christian, salt is related to keeping our flavor. Does that mean that we should remain distinct from the general population? Christians are to impart God's grace, perhaps somewhat like babies were salted in Ezekiel's time.
Salt preserves and flavors. These uses were well known in Bible times. A use that they probably didin't think about was that salt retards freezing. As I write, there is lots of crystallized salt on roads and sidewalks nearby. Christians, too, should be warm-hearted.
There are several Biblical references to the Salt Sea, which we now call the Dead Sea. (It has a high salt content.)
For a lot more about salt, see the Wikipedia article.
