You are the salt of the world, but if salt has lost its taste … [Matthew 5:13 ESV]
Salt has an essential characteristic. It is salt. Sodium chloride. It is made of two chemicals, sodium and chlorine. Take away one of the chemicals leaving the other and it is not salt.
Christians also have essential characteristics, though these are not chemical but spiritual and eternal. Jesus is using an analogy to differentiate between those who are His and those who are counterfeit. Those who are His carry within the morphe of a Christian. They have that which makes a Christian a Christian. Those who do not have the morphe of a Christian may try to manufacture a substitute but will never actually succeed. God is not fooled.
In ancient times salt was hardly ever pure, depending upon its source and the integrity of the person gathering and selling the substance. It would naturally contain other elements as impurities. Gold in salt is an impurity. This doesn’t mean the salt is not salt but that it is salt and something else not salt.
Salt dissolves in water. When the impure batch of stuff claimed as salt is exposed to the weather or humidity the actual substance salt dissolves leaving the impurities which do not dissolve. Salt loses its taste because what is left is everything mixed in which is not salt. Jesus uses the word “lost” in Matthew 5:13 which means to become simple, to lose intelligence, be compromised in the ability to think, or to lose savior. Salt is salt, and when the bags of stuff called salt loses the salt what is left is tasteless and worthless. The more of the worthless stuff mixed in with the salt the easier it is for the actual salt to leech out. What is left can never do what salt is created to do.
For the sake of the discussion let us say salt is a symbol for righteousness, even though righteousness is much more. Because of the image of God in each person, everyone has a sufficient understanding of righteousness. All know the difference between right and wrong and are capable of identifying the measure or standard for their actions and attitudes, the thinking of their hearts. They may not want to recognize God as the ultimate measure for their behavior, or use the term “righteousness” but all know guilt intimately.
Those who are truly salt have God’s righteousness embedded within and covered without, through the sacrifice of Jesus Christ and the indwelling of the Holy Spirit. Those who are not salt have created a self-righteousness, seeking to justify themselves according to the acceptable standards of the world. God is the Eternal Taster and He knows when the salt of righteousness is present and when it is lacking.
Jesus takes it further. No analogy will perfectly describe or define the actual. He is giving those who are His, and the world, a warning about the need and uses of righteousness. He hates unrighteousness and expects the citizen of His kingdom to hate sin as well, while loving the truth. He expects those who are His to hunger and thirst after righteousness. He says those who are His will stand for righteousness when persecuted because of Him, the Giver of Righteousness. Every statement implies His work in the Believer and their work for Him, the evidence of ownership. What owner keeps anything which is useless? Even hoarders see their stuff as valuable to them. Either a person assigns value or they recognize the value assigned by God. Those who think they own themselves, and act like God has no ownership, are still owned by Him and He will do with them as he pleases.
Not everyone who says to me, “Lord, Lord,” will enter the kingdom of heaven, but the one who does the will of my Father who is in heaven. On that day many will say to me, “Lord, Lord, did we not prophesy in your name, and cast out demons in your name, and do many mighty works in your name?” And then will I declare to them, “I never knew you; depart from me, you workers of lawlessness.” [Matthew 7:21-23 ESV]
God will look at the evidence of His ownership recognized by those who are His. Do not interpret these verses as something we do under our own power, from our own direction, while in the world. It is too easy to remove God from the equation of our lives. The tugs and pulls of the world, our own flesh, and Satan, assault us every moment, seeking to compromise our effectiveness for God. These assaults are failed unless we give them permission to succeed. The more we allow the world, our own flesh, and Satan to compromise who God is making us the more unrighteousness is mixed with God’s righteousness. I am not suggesting any who are His can at sometime be not His, or lose their salvation. I am questioning the perception of those who think they are saved, by their own effort, when they are not. Those who reject the absolute authority of God will pile up evidence of their self-righteousness just as those who humble themselves will show evidence of God’s grace.