Salt and Light

Imagine waking up tomorrow to discover that every Christian on earth had simply vanished. What would happen to your workplace? Your neighborhood? Your city? Would anyone even notice?

Jesus has a shocking answer. He says that if Christians disappeared, the world would immediately begin rotting like meat without refrigeration and plunge into darkness like a city without power. That’s because you are not just a nice addition to the world. You are essential for its very survival.

In Matthew 5:13-16, Jesus uses two powerful metaphors to reveal something extraordinary about your identity. This morning we’ll discover that being a Christian isn’t about trying harder to make a difference. It’s about understanding who you already are and living that out.

Christians are the essential preserving force in a decaying world.

Look at verse 13. “You are the salt of the earth.” Notice Jesus doesn’t say “You should try to be salt.” He declares with absolute certainty that you ARE the salt. This isn’t about what you might become if you work really hard. This is about what you already are because of Jesus.

In Jesus’ day, salt was literally a matter of life and death. There were no refrigerators, so people used salt to preserve food. Without salt, meat would rot within hours in the Middle Eastern heat. Entire families would face starvation if their food preservation failed. Salt was so valuable that Roman soldiers were sometimes paid with it, giving us the phrase “worth his salt.”

The English word “salary” does derive from the Latin word salarius, which is related to sal (“salt”). The term salarius originally referred to the allowance given to Roman soldiers to buy salt, known as salarium. Salt was so crucial in ancient times that it was sometimes used as a form of payment or linked to wages, especially for Roman soldiers and workers. Over time, salarium evolved to mean a fixed payment or stipend in general, giving us the modern word “salary.”

But salt does more than preserve. It actively prevents corruption. It penetrates food and acts like a moral antiseptic. This reveals something necessary to understand about the world’s condition. The fact that Jesus calls us salt implies rottenness in the earth. It implies a tendency toward pollution and becoming foul and offensive. That’s what the Bible says about this world. It is fallen, sinful and bad. It tends toward decay. The second law of thermodynamics (the law of entropy) doesn’t just prove true for energy, but it does for spirituality. All things drift toward moral decay in the human soul when not sustained by the redeeming power of Jesus’ blood.

Think about what’s happened throughout history when Christianity has been the preserving salt in society. Christians started the first hospitals. They founded the first universities. They created orphanages and care for the poor. They led the fight to abolish slavery. They championed women’s rights and workers’ rights. They established public education systems. They pioneered scientific research because they believed in an orderly God who created an orderly universe. The Red Cross, the Salvation Army, countless relief organizations, all of these came from Christians who understood they were called to be salt in a decaying world.

We see this playing out in our own culture. As Christian influence has waned, we’ve watched moral standards crumble. We’ve seen the breakdown of the family, the loss of respect for human life, and the rise of relativism where everyone does what’s right in their own eyes. Without salt, decay is inevitable.

John A. Huffman, Jr describing the body of Christ said "This sanctuary can be a salt shaker. You can come in here once a week, have a lot of fellowship with all the other salt and think your job is accomplished. Instead, God wants to pick up this sanctuary and shake you out all over this city. He has brought you together as His salt only to scatter you. He wants you to be an influence for Jesus."

The Greek construction here also emphasizes exclusivity. It’s as if Jesus is saying “you and only you” are the earth’s salt and the world’s light. This isn’t about humanity in general. It’s specifically about Jesus’ followers. Christian, you are God’s preserving agent in a world that is naturally decaying.

As John Stott points out, “And when society does go bad, we Christians tend to throw up our hands in pious horror and reproach the non-Christian world; but should we not rather reproach ourselves? One can hardly blame unsalted meat for going bad. It cannot do anything else. The real question to ask is: where is the salt?”

Christians must maintain their distinctiveness or become spiritually useless.

But Jesus adds a sobering warning in this verse. “But if the salt has lost its taste, with what can it be salted? It is no longer good for anything, except to be thrown out and trampled underfoot.”

When contaminated salt loses its saltiness, it becomes worthless. It can’t be unmixed with the impurities. It’s literally thrown on roads to be trampled. I even read that it’s no good for even manure. The spiritual application for us is devastating. When Christians become contaminated by worldly values, they lose their preserving influence. If Christians become assimilated to non-Christians and contaminated by the impurities of the world, they lose their influence. As John Stott puts it, “The influence of Christians in and on society depends on their being distinct, not identical.”[1] The world needs us to be different, not similar.

The prominent thrust of this passage is distinction. Here’s the thing though: We are to be distinct yet not distant. We are to be separate yet not solo. We are to be holy yet not hermits. We are not to be of the world yet we are to be in the world.

If your theology causes you to retreat from the world, you’ve got it wrong. This Sermon on the Mount is a manifesto of kingdom living. And we are to be a people who advance the kingdom. The world is rotting and is in darkness. If we don’t pursue the world with the love of Christ, we are showing the world we care very little about their well-being. We’d rather be clean than mess with rotten things. We’d rather be safe than risk getting hurt in the dark. That’s not what Jesus taught. And that’s certainly not what Jesus lived.

Martyn Lloyd-Jones warns us that “there is nothing in God’s universe that is so utterly useless as a merely formal Christian.”[2] Wow. That sounds mean. But it’s true. A Christian without distinctiveness is like salt without saltiness, completely useless for what it was made to do.

There’s a double meaning in the Greek word for “loses its taste.” It’s both “losing flavor” and “becoming foolish.” Paul uses the same root word when he writes the word fools in Romans 1:

21 For although they knew God, they did not honor him as God or give thanks to him, but they became futile in their thinking, and their foolish hearts were darkened. 22 Claiming to be wise, they became fools…” (Rom 1:21-22).

This literally can be translated, “Claiming to be wise, the became tasteless.” They lost their savor. The phrase “trampled underfoot” is the strongest possible condemnation. In ancient Palestine, contaminated salt residue was literally thrown on roads where people and animals would walk on it. It went from being precious enough to pay soldiers with to being worthless road material. I don’t want that to be able to be said of me.

Christians are the illuminating presence in a dark world.

Jesus shifts metaphors in verse 14. “You are the light of the world.” This phrase is extra powerful because Jesus uses this exact title for himself in John 8:12. You are light not because you generate it, but because you reflect Christ’s light. Just as the moon has no light of its own but reflects the sun’s brilliance, you shine with Jesus’ radiance.

Why does the world need light? Because it’s in darkness. Despite all our scientific progress and technological advancement, we still see moral confusion, relational brokenness, spiritual emptiness, and the search for meaning in all the wrong places. The “Enlightenment” has not brought the world light. Only the gospel of Jesus can do that.

The absence of light makes darkness genuinely threatening. To understand how precious light was, imagine a world without hundreds of watts of electric power at your instant disposal. In that kind of total darkness, even a small flame becomes precious beyond measure. Sara and I went on a day date to Bowling Green on Friday and went to Lost River Cave. They have lights all through this cave, but at one point, the guide turns off the lights to his boat so you can get a good feel of the darkness. When there’s no light it’s pitch black. But even the smallest light seeps in and dispels darkness. Darkness cannot overcome light.

And Jesus is the light of the world. John 1 shows us beautifully that Jesus, the Light, has come into the dark world, and the darkness has not overcome Him (John 1:5).This metaphor of light naturally connected with Jewish expectations about the Messiah bringing light to the nations, as Isaiah prophesied about God’s servant being “a light to the nations” (Is 42:6; 49:6) The world needs the light of Jesus, and Jesus tells us how it come. He says it comes through his disciples.

Jesus gives two illustrations in verses 14 and 15. “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.”

The first illustration, a city on a hill, emphasizes community visibility. Palestinian cities were built on hills for defense, and their lights were visible for miles. Jesus doesn’t tell us the city He is thinking of here, but many people think it is the city of Susita (Hippos). It is hard to miss a city that is built atop a hill. The light from the city is reflected off the clouds, and the night, once perfectly black, is no longer quite so desolate. It’s just like light pollution from cities now. The light is so powerful it drowns out even the stars in the sky. Likewise Christians who let their light shine can’t be hidden, and the good light they shine around pushes back the darkness which would otherwise be absolute.

The second illustration brings it to the household level. The “bowl” was a grain measure holding about nine liters, large enough to completely hide a lamp. The oil lamps of that era were shallow bowls with wicks. You would, of course, light a lamp in order to be able to see in your house.

The application isn’t about shining in your home necessarily, but your light of Christ should start shining there. Spurgeon says it pointedly like this: “The text says that the candle gives light to all that are in the house. Some professors give light only to a part of the house. I have known women very good to all but their husbands, and these they nag from night to night, so that they give no light to them. I have known husbands so often out at meetings that they neglect home, and thus their wives miss the light.” It must start in our homes, but it must spread to the world.

 The absurdity of what Jesus is saying here is the point. Who lights a lamp to hide it? Nobody! A lamp is lit in order that it may give light to all that are in the house. There is no other purpose in lighting a lamp. Yet that’s exactly what Christians do when they try to keep their faith invisible. Sinclair Ferguson says it like this: “A community of Jesus which seeks to hide itself has ceased to follow him.”[3] We can’t claim to follow Jesus while trying to be invisible. The very nature of authentic Christianity makes hiddenness impossible and unfaithful.

Your faith is personal, yes, but it is not private. Spurgeon further said, “Christ never contemplated the production of secret Christians, – Christians whose virtues would never be displayed, – pilgrims who would travel to heaven by night, and never be seen by their fellow-pilgrims or anyone else.” But what do we shine? We shine Jesus. We reflect God’s glory.

Christians shine through good works that glorify God alone.

Verse 16 gives us the final application. “In the same way, let your light shine before others, that they may see your good deeds and glorify your Father in heaven.”

We are not saved by good works, but we are saved for good works (Eph 2:10). Notice the careful progression. Let your light shine  they see your good deeds  they glorify your Father. The goal isn’t “personal recognition but God’s glory.”[4] People should see our good deeds and think about our Father in heaven, not about how awesome we are. We tend to be glory thieves, though. God deserves ALL the glory, and we try to take some for ourselves. How dare us! He must increase, and we must decrease! (John 3:30)

The Greek word for “good works” doesn’t mean generic acts of kindness. It refers to works that are not only good in effect but beautiful in character. Works that are intrinsically praiseworthy. These flow directly from the Beatitudes character Jesus has just described in the previous verses.

Letting your good works shine seems to create a tension with Jesus’ later teaching about not practicing righteousness to be seen by others (Matt 6:1). But there’s an important difference. The flashy performance of religious acts in order to win applause is not at all the same thing as a life of visible goodness lived in the public arena so that people can’t help being drawn to God. The effect and the intention of the former is so that people will look at you as good and godly. The result of the latter is the glory of God.

It's worth noting that this is the first time in Matthew that God is called “Father.” When people see authentic Christian living, they don’t just admire human virtue. They don’t just think, “Wow, that’s such a good person.” No, they recognize a divine Father who could produce such transformation in his children.

You are salt. You are light. Not something you’re trying to become. It’s who you are right now because of Christ. The question isn’t whether you’ll have influence, but what kind. Will you be effective salt that preserves, or contaminated salt that’s worthless? Will you shine as bright light, or hide under a bushel? The key is living authentically as who Christ has made you to be.

Don’t hide that light. Don’t lose that saltiness. The world depends on it. More than that, God’s glory depends on it. You are his essential preserving and illuminating presence in a world that desperately needs both. The question is whether you’ll embrace that identity and live it out boldly, or whether you’ll blend in and become spiritually useless.

The choice is yours. But remember this. If you don’t shine, who will? If you don’t preserve, what’s left to stop the decay? You are the salt of the earth. You are the light of the world. Live like it.

[1] John Stott, The Message of the Sermon on the Mount (IVP Academic, 1978), 42.

[2] D. Martyn Lloyd-Jones, Studies in the Sermon on the Mount (Wm. B. Eerdmans, 1959), 173.

[3] Sinclair B. Ferguson, The Sermon on the Mount: Kingdom Life in a Fallen World (Banner of Truth, 1987), 61.

[4] R.T. France, The Gospel of Matthew, The New International Commentary on the New Testament (W.B. Eerdmans, 2007), 177.