These are characteristics which both signify the Blessings, and the Judgments of God. In fact, it is the very judgment of God which makes a person good or righteous in His sight. i.e., the judgment for our sins were laid upon Christ, and through His being judged in our stead, we were made good or virtuous.

This is the same principle as fire both being illustrated in scripture as a blessing (as in the baptism by Fire, or refined by fire), and as God's judgments (as in the lake of fire). When we come to understand just how we were made righteous, we understand that the Christians' righteousness, and his judgnt, is intimately related.

It is thus not curious that God, almost from the beginning, used the signification of salt as a figure of the Covenant Promise which He has with His chosen people.
Leviticus 2 :12-13
As for the oblation of the firstfruits, ye shall offer them unto the LORD: but they shall not be burnt on the altar for a sweet savour.

And every oblation of thy meat offering shalt thou season with salt; neither shalt thou suffer the salt of the Covenant of thy God to be lacking from thy meat offering: with all thine offerings thou shalt offer salt.

Salt cannot be lacking from the sacrifice because it signifies the virtue of the sacrifice. It is the flavor which makes the meat good, or gives it it's savory or good taste.
Job 6 :6
Can that which is unsavoury be eaten without salt? or is there any taste in the white of an egg?
Salt makes the meat tasty. That sacrifice is equated to Christ, and it was the salt that made the meat good. This is equating the salt which makes the sacrifice good, to the virtue or righteousness of Christ, which makes us good.

That is why God decrees that the sacrifice was to be seasoned with salt, that no sacrifice should be lacking salt. It is why it is called, The salt of the Covenant. It is the savor of the sacrifice, the righteousness of Christ, which is the foundation of the Covenant. Salt is at the heart of the Covenant both in judgment, and in the virtue of Christ. A sacrifice without salt (without virtue) would not suffice, signifying Christ had to be the lamb that was without sin, that through judgment we could also be made virtuous!

2nd Corinthians 5 :21
For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him.
The virtuous sacrifice, judged for us, that we could be made virtuous or righteous in Him. the sacrifice, seasoned with salt.

Mark 5 :28-30
For she said, If I may touch but his clothes, I shall be whole.
And straightway the fountain of her blood was dried up; and she felt in her body that she was healed of that plague.
And Jesus, immediately knowing in himself that virtue had gone out of him, turned him about in the press, and said, Who touched my clothes?

When this woman touched Christ, His virtue (righteousness) healed her, just as it does every sinner who comes to him. It is His virtue which is the savor of the sacrifice, and this is signified by the salt. When Christ was judged of God for our sins, we became the righteousness of Christ, in Him. We were healed by Christ's virtue, just as this woman was healed by it.

Therefore are we also the salt (righteousness) of the earth, in Him. It is because of Christ's virtue, now in us, that God calls us both the Light of the world, and the Salt of the earth. The two significations of Christ's righteousness.
Matthew 5 :13-14
Ye are the salt of the earth: but if the salt have lost his savour, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men.
Ye are the light of the world.

A city that is set on an hill cannot be hid.
Jesus is here giving us a contrasting view of the man of God with Christ in him, and the man who has fallen away from God, and has no virtue. Note that if the salt have no savor (no virtue), it is good for nothing. For it is the savor which is the goodness! The savor signifies the good or righteousness. In this verse we are warned not so much of our duty to salt the world, but to see that our salt is genuine, having a real flavor.

In other words, we make our calling and Election sure! The previous verses (matt. 5 :11-12) set the context of Christians being reviled, persecuted, and having all manner of evil spoken against them, and it is in this context that in verses 13 and 14 we are warned not to lose our saltiness. Context is important!

In Christ only can we be the salt of the earth, having flavor or virtue to go forth with the gospel, righteously. In Christ only can we be the Light of the world to go forth in righteousness, the gospel shinning, that many will not walk in darkness. Covenant- breakers who cease doing God's work is like salt which has lost it's savor.

Apostasy, or the departing from the faith, is the inevitable result. This salt (without virtue of Christ) is savourless, unfit for use of God, and good for nothing but to be trampled upon by men. Rather than salt of savor, it has become salt of Judgment. Salt loosing it's flavor is salt which has lost all it's goodness. This an*logy is the same one as Jesus uses of a light which has been put under a bushel or bed.

In other words, it's made useless! No Christian should hesitate to salt the earth, or to let his light shine, for fear of not being popular, or being reviled, hated, or persecuted by man. God says blessed are those who for the sake of Christ endure these things. These two figures of light and salt, are synonymous.

Matthew 5 :13-16
Ye are the salt of the earth: but if the salt have lost his savour, wherewith shall it be salted? it is thenceforth good for nothing, but to be cast out, and to be trodden under foot of men.
Ye are the light of the world. A city that is set on an hill cannot be hid.
Neither do men light a candle, and put it under a bushel, but on a candlestick; and it giveth light unto all that are in the house.

Let your light so shine before men, that they may see your good works, and glorify your Father which is in heaven.
Our good works are the light of the world, and our Good works are the Salt of the earth. It is the good of Christ in us (Philippians 2 :13 , Hebrews 13 :21 ), not our own. It is the virtue of Christ, which is the salt of the Covenant that Leviticus addressed! The Promise or Covenant of Christ was confirmed, or given strength (heb. 9 :17), by the judgment of the sacrifice Lamb.

1st Peter 2 :24
Who his own self bare our sins in his own body on the tree, that we, being dead to sins, should live unto righteousness: by whose stripes ye were healed.
It is by His bearing our sins, and His being judged of God for them, that we are healed. And that judgment and healing, is by the signification of salt. The sign manifested in such illustrations as in 2nd Kings.

2nd Kings 2 :21
And he went forth unto the spring of the waters, and cast the salt in there, and said, Thus saith the LORD, I have healed these waters; there shall not be from thence any more death or barren land.
There we see the signification of salt used for the healing of the waters, that there not be any more death or barren land. This is the marvelous spiritual figures which God places in His Holy Word.

One salt makes the land barren, and another salt heals the land that it not be barren. The figure of salt is inseparably tied to both the healing of the nations, and the judgment of the nations. For truly, because of God's perfect justice, you can't have one without the other. Without judgment, there would be no forgiveness.