Salt of the Earth
Salt: permanence(unchanged)- loyalty - durability -fidelity-usefulness-value- and purification.

Salt was a scarce and expensive commodity and its value was as much as gold and silver. Salt was used as currency. To sit above or below the salt identified your class(importance) for example seating arrangements at a feast, according to one's rank(class)(importance). To not to be worth one's salt was a great insult.

I would like to draw your attention to Matthew 5:13

When this was being said by Jesus during The Sermon on the mount. Jesus was addressing the common people(lower class)(fishermen)(shepherds)(labours) that they where worthy and virtuous.

Read Matthew 5:13

(Ye) are the (salt) of the earth:
1The beliver: the faithful
2 value(soul) what God values (virtue)(faithful)

But if the (salt) have lost his (savour), wherewith shall it be (salted)?
1value/beliver/virtue
2faith/hope/charity/knowledge Greek and Aramaic "loses it savour" to become foolish.
3 usefulness (doing the will of God)(spreading the gospel)

It is thereforth good for nothing, but to be (cast out), and to be (trodden) under foot of men.
1force to get out/go away/expelled.
2 trampled/crushed

Jesus' point in talking about salt is this: if we lose our value (salt)(faith)(usefulness) then we are unhelpful to the kingdom and Gods work in the world. As believers it's our duty to spread the gospel how did the gospel come to us? By someone preaching the gospel.

Leviticus 2:13 covenant of salt. Sacrifice- purify- only worthy of pure offerings the best at a cost.

2kings 2:21 pervsering- purifying

Job 6:6 being of faith or becoming faithless(useless)

Mark 9:49-50 faith and virtue

Luke 14:34-35 usefulness and lack of faith.

2 Peter 1:3-8 faith-value- knowledge - usefulness - hope- charity- love