How can salt use its saltiness? Didn’t Jesus know basic chemistry?
Matthew: 5:13 You are the salt of the earth. But what good is salt if it has lost its flavor? Can you make it salty again? It will be thrown out and trampled underfoot as worthless.
If salt loses its saltiness, then it’s no longer salt.
There are a couple of ways that this can happen: salt can be diluted, dissolved and adulterated. Add water, and it all washes away. Add a mysterious white powder that looks like salt but isn’t, in an attempt to con your buyers, and suddenly you don’t have pure salt any more. The salt would have lost some of its flavour.
Back in Jesus’ time, salt was highly valued as a flavouring and a preservative. Roman soldiers were paid in salt—it’s where we get the word salary from. But most salt was rock salt, mined at great expense from salt deposits, and less pure than today’s table salt (it contained more than just sodium chloride). If stored badly, for example through exposure to rain, dust or humidity, it could easily become worthless. And given its high value, any loss of quality would have been devastating. Whatever Jesus’ knowledge of chemistry, He would have known the practical realities of His times.
Salt was symbolic as well as practical. The Law required all offerings to be seasoned with salt.
Leviticus 2:13 Season all your grain offerings with salt to remind you of God’s eternal covenant. Never forget to add salt to your grain offerings.
Lose the salt, lose the reminder of God’s covenant. The sacrifice would also be unacceptable.
Lose your own saltiness, and you’ve lost your value to the people around you, and you’ve also lost your own living reminder of God’s promise of eternal life through Jesus—the new covenant.
How do you keep your saltiness? By following Jesus without compromise.
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