'Salt' symbolizes the desire of truth and good to be conjoined with each other. So, a salt can conjoin water, which corresponds to truth, with oil, which corresponds to good.

Salt can also have a negative meaning. 'Lot's wife becoming a statue of salt' signifies all the good of truth being vastated, or laid waste, in the church that Lot represented. In that story, Lot's wife represented a form of 'truth' that turned itself away from 'good,' and looked instead to doctrinal matters. Because 'salt' can signify vastation, and 'cities' signify doctrinal aspects of truth, in old times they sowed cities with salt when they were destroyed to prevent them from being rebuilt, as in Judges 9:45

(References: Arcana Coelestia 10300)

10300. 'Salted' means the desire which truth has for good. This is clear from the meaning of 'salt' as desire belonging to the love which truth has for good, dealt with below, so that 'salted' means something in which that desire is present. The reason why the desire which truth has for good needs to be present is that this desire causes the two to be joined together; for to the extent that truth desires good it becomes joined to it. Truth and good joined together is what is called the heavenly marriage, which constitutes heaven itself with a person. Therefore when the desire for them to be joined together exists within the worship of God, within every single part of it, heaven - and accordingly the Lord - is present there within every single part. This is meant by the requirement for the incense to be salted. 'Salt' receives this meaning from its conjunctive properties; for it makes ingredients all combine and consequently brings out their flavour. Indeed it causes water and oil to combine, which otherwise do not combine.

[2] When it is known that 'salt' means the desire for truth and good to be joined together it may be seen what the Lord's words in Mark mean,

Everyone will be salted with fire, and every sacrifice will be salted with salt. Salt is good; but if the salt becomes tasteless, how will you season it? Have salt in yourselves. Mark 9:49-50.

'Everyone will be salted with fire' means that each person must have a desire that is present as a result of true love. 'Every sacrifice will be salted with salt' means that the desire present as a result of true love must exist within all worship. 'Tasteless salt' means a desire present as a result of a love other than that true love. 'Having salt in themselves' means possessing truth that has a desire for good.

Love is meant by 'fire', see 4906, 5071(end), 5215, 6314, 6832, 10055.

Worship in general is meant by 'sacrifice', 922, 6905, 8680, 8936.

Can anyone without knowledge of what 'fire' means, or what 'salt' and 'being salted' mean, know what 'being salted with fire' means, why a sacrifice had to be salted, or what the command to have salt in themselves means?

[3] Something similar occurs in Luke,

Any of you who does not renounce all his possessions cannot be My disciple. Salt is good; but if the salt is made tasteless, by what will it be seasoned? It is fit neither for the land nor for the dunghill; people will throw it outdoors. Luke 14:33-35.

'Renouncing all their possessions' means loving the Lord above all things, 'possessions' being what is a person's own. 'Tasteless salt' means desire that springs from the proprium or self, thus from self-love and love of the world. This kind of desire is meant by salt that is tasteless, fit for nothing, as also in Matthew,

You are the salt of the earth; but if the salt is tasteless, by what will it be made salty? It no longer has any use, except to be thrown outdoors and trodden down by people. Matthew 5:13-14.

[4] The need for all worship to contain truth that has a desire for good is also meant by the requirement that every offering of a minchah should be salted, and that the salt of Jehovah's covenant should be on every offering, Leviticus 2:13. By 'the minchah and offering' which compose the sacrifice worship is meant, as above; and the salt is called in that verse 'the salt of Jehovah's covenant' because 'covenant' means a joining together, see 665, 666, 1023, 1038, 1864, 1996, 2003, 2021, 6804, 8767, 8778, 9396, 9416. Also desire is the actual ardour that flames from and so is an extension of love, and love is spiritual togetherness.

[5] Just as truth's desire for good has the capacity to link things together, so falsity's desire for evil has the capacity to separate them; and that which has the capacity to separate them also has the capacity to destroy them. For this reason 'salt' in the contrary sense means the destruction and laying waste of truth and good, as in Jeremiah,

Cursed is the man (vir) who makes flesh his arm. He will not see when good comes; but he will inhabit very hot places, a salt land which is not inhabited. Jeremiah 17:5-6.

'Making flesh his arm' means trusting in himself, in his proprium, and not in the Divine, 10283; and since the proprium consists in loving self more than God and the neighbour, self-love is what those words describe. This is why it says that he will not see when good comes, and that he will inhabit very hot places and a salt land, that is, will lead a life ruled by foul kinds of love and their desires, which have destroyed the Church's goodness and truth.

[6] In Zephaniah,

It will be like Gomorrah, a place abandoned to the nettle, and a saltpit, and a waste forever. Zephaniah 2:9.

'A place abandoned to the nettle' stands for the ardour and passion in a person's life that spring from self-love. 'A saltpit' stands for the desire falsity possesses; and because this is destructive of truth and good, the expression 'a waste forever' is used. The reason for its being said that 'it will be like Gomorrah' is that Gomorrah and Sodom mean self-love, 2220.

[7] Where it said at Genesis 19:26 that Lot's wife was turned into a pillar of salt because she turned her face towards those cities, the meaning was the laying waste of truth and good; for in the internal sense 'turning the face' towards something means loving it, 10189. This explains why the Lord says,

Let him not return to the things behind him. Remember Lot's wife. Luke 17:31-32.

And in Moses,

Its whole land will be brimstone and salt, and a burning, as at the overthrow of Sodom and Gomorrah. Deuteronomy 29:23.

Here, as also elsewhere in the Word, 'land' is used to mean the Church, see in the places referred to in 9325.

[8] So it was that cities which were not to be inhabited any longer were sown with salt after they had been destroyed, Judges 9:45.

From all this it is evident that in the genuine sense 'salt' means the desire that truth has for good, thus its conjunctive power, and in the contrary sense the desire that falsity has for evil, thus its destructive power.

[9] Anyone therefore who knows that 'salt' means truth's desire for good and the force that joins the two together is also able to know what is meant where it says that the water of Jericho was healed by Elisha, by his throwing salt into its source, 2 Kings 2:19-22. For Elisha, like Elijah, represented the Lord in respect of the Word, 2762, 8029; 'water' means the truths of the Word, 'the water of Jericho', and in like manner 'the source' of that water, meaning the truths of the Word in the literal sense; and 'salt' means the desire truth has for good, the joining together of the two, and consequent healing.