Useless Saints are a Contradiction in Terms Text: Matthew 5:13-16
Introduction: The Christian's Potency
We have come to a hinge point in the Sermon on the Mount. Having just laid out the character of the Christian in the Beatitudes, the Lord Jesus now turns to describe the effect that such a Christian is to have on the world. The Beatitudes are not a list of virtues for a quiet, cloistered life. They are the character traits of a spiritual navy seal, the kind of man who upends kingdoms. And so, immediately after describing the blessedness of the persecuted, Jesus tells His disciples what their function in the world is. It is not to be withdrawn, not to be hidden, not to be irrelevant. It is to be potent. It is to have an effect.
The world in its natural state is twofold: it is corrupt and it is dark. It is rotting, and it cannot see. Into this decay and this gloom, God sends His people. And He gives them two metaphors for their assigned task: they are to be salt, and they are to be light. Notice that Jesus does not say, "You should try to be the salt of the earth," or "I'd like you to consider becoming the light of the world." He says, "You are the salt of the earth... You are the light of the world." This is a statement of fact, a declaration of identity. This is what you are. The only question is whether you will be what you are, or whether you will become a walking, useless contradiction.
Our secular age wants Christianity to be a private hobby, something you do on a Sunday morning that has no bearing on Monday's business or Tuesday's politics. They want a toothless, declawed, tasteless, and dim faith. And tragically, much of the modern church has been all too willing to comply. We have traded our salty potency for cultural respectability and hidden our light under the bushel basket of pietistic retreat. But Jesus tells us here that a Christian who has no preserving, flavoring, illuminating effect on the world around him is as useless as salt that isn't salty. It is good for nothing. This is a hard word, but it is a necessary one. We are not called to be liked; we are called to be effective.
The Text
“You are the salt of the earth; but if the salt has become tasteless, how will it be made salty again? It is no longer good for anything, except to be thrown out to be trampled under foot by men.
“You are the light of the world. A city set on a hill cannot be hidden; nor does anyone light a lamp and put it under a basket, but on the lampstand, and it gives light to all who are in the house. Let your light shine before men in such a way that they may see your good works, and glorify your Father who is in heaven.”
(Matthew 5:13-16 LSB)
The Preserving Power of Pungent Saints (v. 13)
We begin with the first metaphor:
“You are the salt of the earth; but if the salt has become tasteless, how will it be made salty again? It is no longer good for anything, except to be thrown out to be trampled under foot by men.” (Matthew 5:13)
In the ancient world, salt was not just a seasoning for your food. We hear this and think of a salt shaker. But its primary use was as a preservative. Before refrigeration, if you wanted to keep meat from putrefying, you would rub it with salt. Salt arrested decay. So when Jesus says, "You are the salt of the earth," He is saying that the presence of Christians in a culture is the only thing keeping it from total moral and spiritual rot. Without the influence of the righteous, the world would descend into utter depravity. The world, left to itself, stinks. Christians are God's divine deodorant.
But salt is also a flavoring. It is pungent. It has a bite. A Christian's presence should make the truth savory. We are to make holiness attractive. But this pungency also means we will be an irritant to the world's open wounds. Salt stings. A faithful Christian presence will necessarily convict the world of its sin, and the world does not like that. If your Christianity has never irritated anyone, you might want to check if it's actually Christianity.
Then comes the warning. "If the salt has become tasteless..." Chemically, sodium chloride cannot lose its saltiness. But the salt used in that day was often impure, mixed with gypsum or other minerals. It could be leached out by moisture, leaving behind a white powder that looked like salt but had no salty effect. It was useless. And what do you do with useless salt? You can't even use it for fertilizer, because it would ruin the soil. You throw it out on the path to be walked on. It is fit only for contempt.
This is a terrifying image of judgment on the compromising, worldly Christian. A Christian who has been leached of his distinctiveness, who has absorbed the values of the world, who no longer has any preserving or flavoring effect, is worthless to the kingdom. He looks like a Christian, he might be in a bag labeled "Christian," but he has no bite. He is good for nothing but to be "trampled under foot by men." When the church compromises with the world, it does not gain the world's respect. It earns the world's contempt. The world knows a fraud when it sees one, and it has no use for a church that simply echoes its own decaying values back to it.
The Unavoidable Witness of a True Church (v. 14-15)
The second metaphor builds on the first, moving from a hidden influence to a visible one.
“You are the light of the world. A city set on a hill cannot be hidden; nor does anyone light a lamp and put it under a basket, but on the lampstand, and it gives light to all who are in the house.” (Matthew 5:14-15 LSB)
The world is not just decaying; it is dark. It is spiritually and morally blind. It is stumbling around in the gloom of its own ignorance and rebellion. Jesus says to His disciples, a ragtag group of fishermen and tax collectors, "You are the light of the world." This is a staggering claim. The light of the world is, of course, Christ Himself (John 8:12). But we are light in Him. We are the moon that reflects the light of the Son. Our job is to shine, to illuminate, to reveal what is true and to expose what is false.
He gives two illustrations of the public nature of this light. First, "a city set on a hill cannot be hidden." A city built on a mountaintop is visible for miles, especially at night when its lights are on. It is an unavoidable landmark. This is what the church is meant to be. Our corporate life together, our worship, our fellowship, our families, our schools, our culture, should be a shining civilization of righteousness that the whole world can see. This is not a call for individual Christians to be little lighthouses all by themselves. It is a call for the church, as a corporate body, to be a visible, alternative society. The goal is not just to get individual souls to heaven, but to build a shining city here on earth as a witness to the nations.
The second illustration is personal. You don't light a lamp and then hide it under a peck measure. That would be absurd. The purpose of a lamp is to give light. You put it on a lampstand so it can illuminate the whole house. The modern evangelical impulse to privatize faith, to make it a "personal matter" between me and Jesus, is the spiritual equivalent of lighting a lamp and immediately shoving it under a bucket. It is a dereliction of duty. We are commanded to be public with our faith, to let it shine in every corner of our lives, our homes, our work, and our communities.
The Goal of Good Works (v. 16)
Finally, Jesus gives the purpose and the method for this shining.
“Let your light shine before men in such a way that they may see your good works, and glorify your Father who is in heaven.” (Matthew 5:16 LSB)
How do we shine? Not primarily through bumper stickers or tracts, though they may have their place. We shine by our "good works." This is not a call to moralism. These are not works done to earn our salvation. These are the good works that are the fruit of our salvation (Eph. 2:10). This is the life of the Beatitudes lived out in public. It is integrity in business, fidelity in marriage, discipline in our homes, justice in our communities, mercy to the poor, and joy in our worship. It is building beautiful things, creating excellent art, pursuing faithful science, and raising godly children. It is the tangible, visible evidence of the lordship of Christ over every area of life.
And what is the goal? It is not our own glory. We are not to shine so that men will say, "My, what wonderful people those Christians are." The goal is that they "glorify your Father who is in heaven." Our good works are to be windows through which the world can see the goodness and greatness of God. Our lives are to be signposts pointing away from ourselves and toward Him. When a non-believer sees a Christian family that is joyful and ordered in the midst of a chaotic culture, or a Christian businessman who is honest when everyone else is cheating, the question should arise, "Why are they like that? What is the source of that life?" And the answer is our Father in heaven. Our lives are to be the evidence. We are exhibits in the case for God.
This means our witness must be both salty and bright. It must be distinct, pungent, and preserving. And it must be visible, public, and beautiful. A secret disciple is a contradiction in terms. A tasteless Christian is a waste of space. A hidden church is a burning lamp under a bowl, starving itself of oxygen and leaving the world in darkness. The command is clear. Be what you are. Be salty. Be luminous. And do it all in such a way that the world, seeing your good works, has no choice but to stop and consider the magnificent God who is your Father.