“You are the salt of the earth; but if the salt has become tasteless, how can it be made salty again? It is no longer good for anything, except to be thrown out and trampled under foot by men.” (Matthew 5:13)
What does Jesus mean by that? (Or in Mark 9:49-50, Luke 14:34, or Colossians 4:6?)
[S]alt has been the best-known food preservative, especially for meat, for many thousands of years…
Salt's ability to preserve food was a foundation of civilization…
Too much or too little salt in the diet can lead to muscle cramps, dizziness, or electrolyte disturbance, which can cause neurological problems, or death.
So is salt good or bad?
Salt is a representation of God's covenant with us (Leviticus 2:13 and Numbers 18:19), specifically of our obedience and God's cleansing. As a representation of God's power, we know salt has the potential for devastation:
‘All its land is brimstone and salt, a burning waste, unsown and unproductive, and no grass grows in it, like the overthrow of Sodom and Gomorrah, Admah and Zeboiim, which the Lord overthrew in His anger and in His wrath.’ (Deuteronomy 29:23)
God's response to sin is wrath. Oversalting. Destruction.
He changes rivers into a wilderness
And springs of water into a thirsty ground;
A fruitful land into a salt waste,
Because of the wickedness of those who dwell in it. (Psalm 107:33-34)
So how can destruction be good? Why would we want to be salt? Why would we want salt in our speech?
Every branch in Me that does not bear fruit, He takes away; and every branch that bears fruit, He prunes it so that it may bear more fruit. (John 15:2)
In the covenant of Christ (Matthew 26:27), God forgives our sins, but He prunes us that we might bear fruit for His glory. Every son He receives He scourges (Hebrews 12:6). The prophet Elisha purified the spring at Jericho by applying a jar of salt (II Kings 2:19-21); by the same application of God's discipline, we are purified - sanctified.
And the Word became flesh, and dwelt among us, and we saw His glory, glory as of the only begotten from the Father, full of grace and truth. (John 1:14)
So like Christ, we are to have grace and truth in us. We are to have the salt of the covenant - the body and blood of Christ - in ourselves, and respond to God's calling to be holy and set apart. In our relationships with those around us, we are not to throw stones (John 8:7) or oversalt those around us, but we are meant to apply salt for cleansing (II Timothy 4:2)… for the preservation of ourselves, our loved ones, our civilization, our world.