The Salt of the Earth

Matthew 5:11-13: Blessed are you when people insult you, persecute you and falsely say all kinds of evil against you because of me. Rejoice and be glad, because great is your reward in heaven, for in the same way they persecuted the prophets who were before you.

You are the salt of the earth. But if the salt loses its saltiness, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled by men.

You are the light of the world. A city on a hill cannot be hidden. Neither do people light a lamp and put it under a bowl. Instead they put it on its stand, and it gives light to everyone in the house. In the same way, let your light shine before men, that they may see your good deeds and praise your Father in heaven.

Salt of the Earth v. Salt of the Sea
There were two main ways to come up with salt in antiquity: salt deposits on or in the earth, otherwise known as crystals, and seawater. The first was quite easy to deal with - all you had to do was grind the hard pile of white stuff, which was often sitting in a pile next to the Dead Sea, into salt, and you wound up with about a 98% purity rate.

The Salt of the Earth: Piles of salt crystals deposited naturally next to the Dead Sea.

Sea salt, created by evaporating seawater, was mixed with impurities that couldn’t be removed. Thus, it could never be as pure as rock salt – ‘earth salt.’

Salt of the earth – rock crystals – can’t lose their saltiness, so Jesus must be talking about a different kind of salt when he says, ‘if the salt loses its saltiness, how can it be made salty again?’

I think Jesus is contrasting purer salt of the earth, which couldn’t lose its saltiness, with impure sea salt.

So Who Gets Trampled?
I’m not sure anybody gets trampled. To make his words more concise, try this: “You are pure salt. But how can impure salt become salty? All it’s good for is the garbage.”

Or, “You’re not trash, you’re the best kind…”
….”You’re the light of the world…”
“You’re a lit lamp….”
“…show your good deeds to men, that they may praise your Father in heaven.”

It makes sense for it to be encouragement, since Jesus just said people will persecute you and tell you horrible things about yourself. And it certainly questions the traditional interpretation that it refers to Christians who have walked away from the faith.

Sources
Aside from that specifically mentioned, my sources were:
Thurmond, David L., A Handbook of Food Processing in Classical Rome, Brill, 2006, pages 234-247

Safrai, Ze'ev, The Economy of Roman Palestine, Routledge, 1994, pages 185-187