Immediately before this passage are The Beatitudes, where Jesus describes the character traits that are going to mark his followers. But if the Beatitudes tell us what our characters as Christians should look like, when Jesus uses these metaphors of salt and light he’s telling us what our influence in the world should look like.

The State of the World
Now currently salt has a bad press, doesn’t it? I have a strong family history of high blood pressure, and mine is a bit uppish, and so the moment I so much as look at the salt on the dining table, let alone stretch out my hand for it, the girls shoot me these accusing glares.

In fact, when we were in Canada we were staying with some friends and he’s an expert on high blood pressure and advises the government on it etc. And his wife was telling me how he’s declared war on a famous brand of soup because of its salt content. Now I might not have thought much more about that until the second week of our holidays when we were camping in the Rockies and this young Belgian guy approached us at dinner time carrying a tin, and asking us if we had a tin opener. So I gave him my Swiss army knife, which he then proceeded to totally fail to open the can with. So I said, ‘give it to me’ – and I opened it for him, and in response he said, and I quote, ‘you’re the hero of the night!’, which not a lot of people say to me it has to be said, but as I handed the can back to him, for the first time I realised it was a tin of this same soup my friend is at war with, and it was all I could do to stop myself from grabbing it back and telling him he can’t possibly eat this poison!

But salt hasn’t always had a bad press. In fact in Jesus day, whilst it was used for flavouring, when most people thought of salt they would have thought of it as a preservative. You see, before the age of fridges and freezers, if you wanted to keep your meat or fish from going off, you’d salt it. And that’s not as alien as you might think, is it. I mean, if you’re South African, think of Biltong, or from North America think of beef jerky. You dry the meat, you cut it into strips and you salt it, and it keeps forever.

But think about the implication of Jesus saying that these first disciples, and you and me as his followers, are the salt of the earth. What does that say about the world? What does it say about cultures and societies, and about the lives of individuals who make up our communities? It’s that they are always at risk of decaying and breaking down and falling apart. That just as meat or fish is at risk of bacteria infecting them and making them go rotten or mouldy, so our cultures and societies and individuals who live in them have this tendency to go rotten and bad, and they’re at risk of influences that bring corruption and decay.

And you know from history that that’s the case. Great empires come and then they go. And once great civilisations lose their way and crumble into the dust of history. And great leaders are discovered to have feet of clay and they fall. And individuals experience breakdown, and life falls apart.

And the Bible tells us that this is exactly what we should expect. In Romans 1 Paul says that when people give up the knowledge of God, when they supress the truth about God and about life, that deep down they really know, then God gives them over to what they want. So societies and individuals turn their back on God and say ‘we don’t want you, we want this’, and God goes, ‘ok, well you can have it and let’s see how it goes with you’. And so we worship sex, and culture is pornified and women are objectified. We worship power and we get rulers, or wannabe rulers, who are demagogues. We worship entertainment and we get reality TV stars and chat show hosts setting the tone.

And just think about the implications of Jesus saying this immediately after the beatitudes. Because it’s the fact that so often we extol the opposite of those character traits that he extols, that make the world the way it is: and we praise the self-made man (though there is no such thing) rather than a poverty of spirit; we think it’s cool to be carefree about life, rather than mourn over sin; we lift up the proud, rather than the meek; we idolise possessions rather than hungering and thirsting after righteousness; we take revenge rather than offer mercy; we feed our lust rather than pursue purity of heart; and we make war rather than peace.

But if Jesus’ metaphor about being salt tells us the world is in decay and always at risk of going bad, what does the metaphor of us being light tell us? That the world is dark. Now, in the Bible, light and dark are often used as a picture for truth and error, of knowing God or of being separated from him. And so Jesus is saying that when it comes to truth, it’s dark out there. That people have this tendency to believe things that are not true, to value highly things that in reality are of small value, to build culture and societies on part-truths and to base their lives on stuff that is untrue.

Now if that’s the diagnosis, what’s Jesus’ solution?

Salt and Light
Look at v13 again, ‘you are the salt of the earth’. Verse 14, ‘You are the light of the world.’

So, if you’re a follower of Jesus, you’re part of the solution. You’re to stop or slow the decay and you’re to bring light to the darkness. You’re to live and work to stop the spread of evil and in its place spread that which is good and true and beautiful. And so it’s not just negative – preventing decay – it’s also positive – spreading good: at home, at school, on campus, in your workplace, in your local community, in the lives of those you’re close to.

The question of course is… how can you be salt? And what does it look like to be light?

Well, I want to give you three things: firstly, it’s about living the beatitudes. A salty Christian, a salty church, a Christian who brings light, is one whose life has been so transformed by the gospel of Christ that they carry with them this flavour of Christlikeness. And they live that life out there in the world, not hidden in a Christian ghetto. Not staying in bags of salt whilst the world rots around them. To be salt is to live out the beatitudes – knowing that you need God above everything else, mourning over the brokenness of sin, growing in meekness, hungering for righteousness, showing mercy, pursuing purity, making peace – living those out, not in a holy huddle, but in the workplace, at the school gate, in messed up people’s lives, because that’s where the rot sets in.

Secondly, it’s about living counter-culturally. You see, the metaphor for light that Jesus uses is fascinating. Verse 14, ‘You are the light of the world. A city set on a hill cannot be hidden.’ Except people tend not to build cities on tops of hills, do they? I mean think when you drive into Valais – all the cities are in the valley – it’s only little villages that are up the mountains. And when we were in Canada it was even more striking – there was nothing at all in the mountains, it’s all down on the plain. Because it’s too difficult, it requires too much labour, the costs are too high, to try and build a city up there, and besides, the rivers are all down here.

So a city on a hill stands out. It stands out because everyone can see it – its light shines for miles around. But it also stands out because people don’t build cities like that – it's counter-cultural. And you and I are going to be light in the dark world when we live counter-culturally: when the way we see and use money and possessions, and position and power, and influence and sex and image is so different from the world that they see it. And living that counter-cultural life spreads the light and it helps delay or stop the rot.

Thirdly, by speaking the truth. You see, if there is this link between light and truth, then sometimes light needs to be put into words. Because that’s the way we communicate the truth. And the world does not just need a preventive – some action to slow the downward spiral - it needs, people need, genuine heart change. And that can only come through the gospel. And so to be light means to speak about the truth of Jesus, of what he has done in your life, of how he’s the answer to your fears and anxieties; your pride and selfishness. And listen how Paul puts it in Philippians 2: ‘Do all things without grumbling or disputing, that you may be blameless and innocent, children of God without blemish in the midst of a crooked and twisted generation, among whom you shine as lights in the world, holding fast to [or holding out] the word of life’ (Php 2:14-16). So how do you shine? By speaking – and speaking the word of life, which dispels the darkness of death.

But it may also, at times, mean standing up and speaking out against some things. Don’t you think it’s interesting that Jesus doesn’t say, ‘you’re the sugar of the world – and you’ve got to sweeten it a bit.’ He says you’re the salt of the earth, and there’s something sharp about salt isn’t there? And so there is about authentic, biblical Christianity. It runs at cross-purposes to the ways of the world, and it clashes with the world. And we’re called to be salt, not sugar, and salt is an antiseptic and antiseptics sting.

I remember as a boy staying at my uncle’s house, and I borrowed one of my cousin’s bikes and cycled down this steep gravel hill just outside, and needless to say I flew over the top of the handlebars and grazed my face and my elbows and shins. And my cousin led me crying to my aunt, who sat me down and told me to be brave and that she would put some antiseptic on the cuts. Except, I didn’t know what antiseptic was, until she started putting it on. And what pain I felt before was nothing in comparison to that! But why did she do it? To stop it getting worse. And because she cared. And sometimes being salt and working to arrest the spread of evil will mean we oppose and say ‘no’ to stuff, not because we’re obnoxious, or haters, but because we love and we care. And sometimes that kind of love stings.

And so being salt and light may carry a cost for you.

Opposition and Attraction
You see, right before this salt and light metaphor, Jesus ends the beatitudes by saying, v10-11, ‘Blessed are those who are persecuted for righteousness’s sake… [and] blessed are you when others revile you and persecute you and utter all kinds of evil against you falsely on my account.’

So Jesus takes it for granted that if you’re his follower, if you’re going to live as salt and light, you will face opposition – because he doesn’t say ‘blessed are you if others revile you’, but ‘when they revile you’. This will happen, Jesus says.

Now, the hard truth is that you can be reviled for reasons other than Jesus, can’t you. You can be reviled because you’re self-righteous; because you really do hate others, because in a superiority fuelled by religion you do look down on others. But that’s not being persecuted for righteousness’ sake or reviled because of Jesus is it? That’s being reviled because you’re a jerk. And being salt and light is not the same as being a jerk. Being salt and light is caring so much about the state of the world and the brokenness of other people’s lives and the crushing effects of sin that you’re prepared to risk losing the respect of others, or your reputation, or financial reward or promotion because you love those who are mangled by sin and darkness.

But when you do love like that – there is this cost of how others will see you and speak of you and think of you. And that can make you withdraw out of fear of the cost. In the Second World War, during the Blitz, when the German bombers rained down their bombs on British cities, a blackout was imposed. Air-raid wardens would go round the streets making sure no lights were showing from the windows, and thick black out curtains would stop light escaping from homes onto the streets outside, for fear that the bombers would find their target. And it’s that same fear, that you might become a target that can make you put up the black out curtains: in Jesus’ words, you hide your lamp under a basket. But lamps aren’t made to be hidden, are they? The whole point of lamps is they’re to shine their light. You put them on stands, not under buckets, Jesus says.

But of course, that’s not the only way we can fail to let the light shine. We can read these beatitudes and see how Jesus would have us be, then look at the world and see how wrong it is, and think – ‘I don’t want to be contaminated by this’, so we withdraw to the Christian ghetto. But that’s no way of being salt and light. Antiseptic is useless at arresting the spread of disease all the time it stays in the bottle. A torch is useless for helping someone lost in the dark find their way to safety unless someone turns it on. As Dietrich Bonhoeffer, one of those brave German Christians who resisted Hitler, said, ‘A community of Jesus which seeks to hide itself has ceased to follow him.’

Then, sometimes we can think that we must become more like the world if we are to be salt and light. That to attract them we should be like them. But that, as Jesus says, is salt losing its saltiness. It’s compromised and contaminated salt. It’s rock salt where all the salt has been washed out and only the rock dust remains, and rock dust is used for pavements and walkways, not antiseptic: v13, ‘It is no longer good for anything except to be thrown out and trampled under people’s feet.’

No – what Jesus is saying is that there is a kind of saltiness, there’s a kind of light, that whilst it will be spoken against by some, others will find it intensely attractive. Verse 16, ‘In the same way, let your light shine before others, so that they may see your good works and give glory to your Father who is in heaven.’ You see, if all we ever get is push back and opposition, we’re probably not being persecuted for Jesus’ sake – we’re probably just being argumentative or socially inept or self-righteously religious. Or, if all we get is the applause of the world, we’re probably compromised and no different from the world. But if we’re getting both flak and seeing people come to faith and giving praise to God for what we do and say, then we’re showing ourselves to be true followers of Jesus.

The question of course is, how can you do that? How can you bring together in your own heart a deep love for the world, whilst recognising and standing against all that is wrong with it? And how can you find the courage to be salt and light when it might cost you?

Christ, the changer of hearts
In Charles Dickens’ book David Copperfield, the main character, David Copperfield, is sent away to a boarding school that is truly terrible. But what makes his experience worse is that he is forced to wear a placard on his back that spells out what he had done wrong that made his cruel step-father send him away in the first place. And the shame of carrying that board around, spelling out his sin, for everyone to see, weighed more upon him than the board itself ever could.

But we could all wear such a board, couldn’t we? That listed all the things we’ve done of which we are or should be ashamed. You see we can look at the world and see all that is wrong with it, but the reality is we don’t have far to look, we only have to look into our own hearts to see we are no different, and our sin and shame is no less.

But the extraordinary thing about Jesus is that, knowing all that, he still comes – for God so loved the world that he sent his son – and he comes and he takes that placard of shame off your back, and he carries it on his own back, and he goes to the cross and he dies there for all the shameful things that we have ever done or wanted to do. And he was shamed for us.

And knowing that, deep down in your heart, changes your heart. It changes the way you see the world and the sin and darkness of the world. Because you know you are no better than the world – you know that you are so rotten Christ had to die for you, to bear your shame. And that kills any self-righteous looking down on the world. And that means that when you do critique or oppose sin or seek to shine light on the darkness of the world, you do so as one deeply humbled by your own need of salt and light.

But you also know that Christ did die for you, that he did lift that placard of shame off your back, and carried it to the cross, and he did it because he loves you. And when you know that he was shamed for you, it changes the way you see any shame or any cost you might experience because of him. You don’t go seeking it, but neither do you run from it. Because what price could you possibly pay that comes close to the price he paid for you?

And in knowing the joy and the forgiveness and the hope that Christ brings into your own life through what he has done for you, you know you have the light the world needs – you have light to give and truth to tell. And you can be the light of the world, and as a church we can be a city set on a hill, when you know that Christ, the light of the world, has shone in your heart and dispersed the darkness.