In the Sermon on the Mount Jesus sets out how the lives of his followers are going to be different from the crowd. The challenging thing, though, about this sermon, is that the difference he’s talking about is not simply outward behaviour. It’s not about making us more respectable, or middle-class, in the eyes of the world. It’s about change at the level of our hearts. And that is deeply challenging, because it gets to the root of who we really are. But it’s also tremendously hopeful. Because it tells you that when Jesus calls you to follow him, he doesn’t leave you where you are.

And that is true for some of the most intimate areas of our lives – in sex and relationships, and personal trustworthiness. Areas where the potential for hurt is huge, but where the potential for blessing is so great.

You see, when we talk about our sexual desires, as Jesus does here, or about adultery and relationship breakdown, we’re talking about stuff that is incredibly sensitive. We all carry scars from our past, and some of us carry open wounds from our present, and perhaps nowhere are those more tender than in these areas. I know that. But more importantly, Jesus knows that. He knows the hurt that has been done to you; he knows the hurt we inflict on others; he knows the mess and the brokenness of our lives. And as we hear him speak this morning, we’re in the presence of the one physician who can heal our wounds and bind up our broken hearts, as well as do the radical heart surgery everyone of us needs.

Four points this morning: faithful in thought, faithful for life, faithful in word, the faithful friend of sinners.

Faithful in Thought
If you remember from two weeks ago, Jesus has just dealt with the 6th of the Ten Commandments – you shall not murder. Now, he moves on to the seventh: v27, “You have heard that it was said, ‘You shall not commit adultery.’” And then he does exactly what he did before and he goes for the heart. Because just as murder germinates in the heart, and begins with hatred, so adultery begins with the eyes, and with the imagination of our hearts. Verse 28, “But I say to you that everyone who looks at a woman with lustful intent has already committed adultery with her in his heart.”

Now, Jesus doesn’t mean here that there is a moral equivalence between a lustful thought and the physical act of adultery. What he’s saying is that God’s law goes far deeper and wider than the physical act. It encompasses what goes on in our minds, as much as in our beds. And you might never have touched another man or woman, and yet have committed heart adultery because you’ve allowed those thoughts to germinate and you’ve given lust a foothold. And faithfulness in marriage, or sexual purity in singleness, is as much about being faithful with your eyes, and imagination, as much as it is with your body.

But, in saying that, there are two dangers which I want to tackle head on before we hear the rest of what Jesus says. Firstly, it's easy to think this is a men-only problem. And it is a huge issue for us guys. Yet the number of women who regularly view porn is rising, and a good-looking guy can still turn your heads in a wrong way. And yet ladies, maybe for you, this isn’t a visual, ‘undressing someone with your eyes’ issue. Maybe for you this is an issue of idolising romance. That you imagine what life would be like with so and so; that the man of your dreams becomes someone other than your man. And rather than a sexual unfaithfulness in the mind, it’s a romantic unfaithfulness in the heart. And of course, you don’t have to be married for this to be a problem. Whether it’s through books or magazines or films, when you’re single and you don’t want to be, romance can become an idol. But whether it’s lust or romance, whether it’s heterosexual or same-sex, whether you’re male or female, none of us can say we’re in the clear on this. As soon as Jesus brings God’s word to bear on our hearts and minds, we’re all sexual sinners.

But the second danger is to throw out the good with the bad. Imagine that one day you come home and you find a squatter, or a burglar, making himself at home in your house. When you throw him out, you don’t also throw your wife out with him, do you? Your wife gets to stay! That’s who the house is for! And the Bible is not prudish about sexual pleasure, and it’s not because God is not. He is the designer and creator of it. He has wired you and designed you and created you in such a way to experience this. Plus, the Holy Spirit inspired the writing of a book in the Bible, the Song of Songs, given over to a beautiful description of the anticipation and fulfilment of sexual desire. And so sexual desire is good, and interest in the opposite sex is good. And imagination, and the powers of your imagination are good. It’s just it’s not for the squatter. It’s for your wife, or your husband. And whilst you kick out the bad, you nurture, and feed, and cherish the good.

But kick out the bad you must, Jesus says. Verse 29, “If your right eye causes you to sin, tear it out and throw it away.”

So, what you and I do with our bodies and our minds, matters, Jesus says. It matters now, but it also matters for eternity: “For it is better” Jesus says, “that you lose one of your members than that your whole body be thrown into hell.” And let’s be clear, because the Bible is clear, that there are some sins so serious that if a Christian commits them it must raise the question of whether they’re a follower of Jesus at all. That unless we see real, deep, genuine repentance and contrition, we should and must cry ‘danger!’ Ephesians 5:5-7, ‘For you may be sure of this, that everyone who is sexually immoral or impure, or who is covetous… has no inheritance in the kingdom of Christ and God. Let no one deceive you with empty words, for because of these things the wrath of God comes upon the sons of disobedience.’

So if this is a problem for you, Jesus says, take radical action now. I mean think about a garden. If the gardener doesn’t want weeds infesting the garden, what does he do with the first one that spouts up? Does he feed it and water it and sing to it? No, he roots it out. So do the same with your heart. Pluck out your eye, cut off your hand. It doesn’t matter what other people do, or watch or say. It doesn’t matter if this isn’t a problem for them. If it is for you – act.

Now, is Jesus talking figuratively? Of course he is. He’s not saying ‘go maim yourself.’ A one-eyed, one handed man still lusts. But don’t dismiss the force of what Jesus is saying by saying, ‘he’s just being figurative.’ He’s also being deadly serious and calling you to get deadly serious with your sin. The eye is the organ of seeing – so don’t look. The hand is the organ of doing – so don’t click. The foot is the organ of going – so don’t go there. If we want to get serious about dealing with lust in our hearts, or the idolatry of romance, there are going to be some films you don’t watch, some sites you don’t visit, some books you don’t read, some magazines you don’t pick up, some TV remotes you don’t touch, some venues you don’t visit, some business trips you don’t take, because you want to honour Christ more than you want to feed your lust. Don’t tolerate your sin. Root it out, Jesus says. You will get to heaven without a TV! You will get to heaven without Netflix! You will even get to heaven without a smart phone! Do whatever it takes, Jesus says.

And personally I have found it incredibly helpful to follow the example of Job, “I have made a covenant with my eyes; how then could I gaze at a virgin?” (Job 31:1). Make a covenant with your eyes, never to look on someone else from a wrong desire. Train your eyes to look away. The moment you find your eyes drawn, physically look away; the moment you find a thought forming in your mind that you know is wrong, rebuke it, take it captive, bring it to obedience to Christ. Will you get it right in one go? No, but with time you will, as you count yourself dead to sin in Christ. In all the visits I made to the hospital mortuary as a doctor, I never once saw a dead man look at a woman wrongly, or engage in a wrong conversation. Why? Because dead men don’t. So count yourself dead, as Paul says. Kill the bad; kick out the squatter. And if you’re married, feed the good, let your passion for your wife, or your husband grow, by nurturing it.

And Jesus says, that kind of faithfulness is not going to be a short-lived thing.

Faithful for Life
In a few years time, if someone were to read a one line email you’ve sent, they wouldn’t have a clue what you were talking about, would they? Unless they also saw the email from the person you were responding to. They need to know the context.

And the same is true for Jesus’ teaching on divorce, here and in Matthew 19. Because there was a debate raging between two rabbinic schools: the school of Shammai and the school of Hillel. And it was a debate as to when a man could divorce his wife. You see, Jesus says in v31, “It was also said, ‘Whoever divorces his wife, let him give her a certificate of divorce.’” And he’s quoting there from Deuteronomy 24:1 where Moses says a man may issue a certificate of divorce to his wife if he finds some indecency in her. And the debate raged around what Moses meant by indecency. Shammai was strict – this was about adultery and sexual unfaithfulness. Whereas Hillel was liberal - a man could divorce his wife for any reason: if a younger model came along, or if she burnt the toast, because that was pretty indecent.

And on the surface, Jesus sides with Shammai: the only grounds for a husband to divorce his wife were if she had been sexually unfaithful. And Jesus does say at least that. But yet again he goes much further. You see, Jesus does not approach the issue of divorce by talking about divorce, but by talking about marriage. Verse 32, “But I say to you that anyone who divorces his wife, except on the grounds of sexual immorality, makes her commit adultery.” Why? Why does a man who divorces his wife, for anything other than sexual immorality make her commit adultery? Because in that culture she would almost certainly remarry, because there was no other way for her to support herself. But if she remarried she would be committing adultery, Jesus says, because she was still married to her original husband. They were still man and wife. In other words, just because this guy gives his wife a piece of paper saying he’s divorced her and she’s free to remarry, does not mean that God sees it that way. He might think his marriage is over; but God sees it very differently. As Jesus says in Matthew 19, “what therefore God has joined together, let not man separate.” You might think you can push her away, Jesus says, you might think it’s over between you, but God doesn’t. God has joined you and he’s joined you for life. And you’re to stay faithful for life. One wife, for life.

And the only reason to break that bond is if it’s broken by adultery. But even then, Jesus differs from the crowd. Because the rabbis commanded divorce in the case of adultery, but Jesus never does. Instead, he allows this one exception for divorce, and later Paul will add a second of abandonment, having already said we should make every effort to be reconciled when relationships break down. In Jesus’ eyes, marriage is this permanent, one flesh union of man and woman. And for all our easy come, easy go relationships, deep down we know this is true. It’s why adultery and divorce hurt so much: your life has been ripped apart.

Now, are there times when separation might be appropriate? Reluctantly, yes, especially when there’s violence involved. But any separation should be to create space for safety and for deep repentance. And it should always be with the Christian hope that reconciliation might be possible. It should never be to walk away from commitment. Interestingly, John Chrysostum, the early church father, tied what Jesus says here about divorce back to the Beatitudes. He wrote: ‘For he that is meek, and a peacemaker, and poor in spirit, and merciful, how shall he cast out his wife? He that is used to reconcile others, how shall he be at variance with her that is his own?’ And today, no doubt, he would say the same to wives as to husbands.

But one last thing about the life-long commitment of marriage. Because you might hear that marriage is life-long and think it’s like walls of a prison – and you’re trapped. But what if those walls are there to protect you? What if, rather than life-long commitment being the walls of a prison, they’re the walls of a garden – that keep the wild animals out, and make it a safe place for kids to play and flowers to grow? When we were in the UK we used to visit a country house with a famous walled rose garden. You would walk through the gate and the beautiful scent of these roses would hit you: kept in by the walls. And the strong walls of life-long, faithful marriage are the boundary that means love and sex and joy and family can flourish. Because you’re safe within those walls, and you’re not looking, or going, anywhere else.

But it’s not just in your thought life, or in your commitment that you’re going to be faithful, Jesus says, but also in what you say.

Faithful in Word
Now when I was a boy we had a neat trick to get out of sticky situations. If you needed to promise someone something, like ‘I promise I’ll give you one of my sweets tomorrow if you give me one of yours today’, but you had no intention of carrying it out, you made the promise and you crossed your fingers behind your back at the same time. And magically, that absolved you of any moral obligation to fulfil your promise. The next day when your friend asked for a sweet you could go, ‘had my fingers crossed! Nah, nah!’ And those crossed fingers meant the ground couldn’t open up and swallow you, and God couldn’t strike you dead, and your friend couldn’t have his sweet.

And believe it or not it’s the spirit of the crossed fingers that lies behind what Jesus says about making vows. You see, when Jesus says in v33, “You have heard that it was said to those of old, ‘You shall not swear falsely, but shall perform to the Lord what you have sworn’, whilst he’s not directly quoting scripture he is summing up the Old Testament teaching on vows. That if you make a vow, you must carry it through.

But what had happened is that the religious leaders had taken that teaching and developed elaborate rules about what kind of vow was binding. And they’d even written a whole tract about it. And basically, it was only those vows that included, or alluded to God’s name that were binding. And if you hadn’t mentioned him, then you had wriggle room, you could break it – provided you didn’t mention God. It was the first century equivalent of, ‘had my fingers crossed!’

And it’s into that duplicity that Jesus speaks, v34: But I say to you, Do not take an oath at all, either by heaven, for it is the throne of God, or by the earth, for it is his footstool, or by Jerusalem, for it is the city of the great king. And do not take an oath by your head, for you cannot make one hair white or black.” In other words, you cannot pretend that your word is not binding because you didn’t mention God, because everything is God’s. Heaven is his. Earth is his. Jerusalem is his. Even the hairs of your head are his.

It’s not how you phrase your vow, or cross your fingers that matters, Jesus says, it’s that you’re one of my followers. You don’t need to pile up words, you simply need to be a person of your word. Verse 37, “Let what you say be simply ‘Yes’ or ‘No’; anything more than this comes from evil.” So if you’re a Christian, you’re to be a person of integrity, whose word means something; whose words can be believed; who is faithful in what you say.

But as we finish, if we’re honest, we can all look back over our lives and see multiple ways we’ve failed to live up to Christ’s standards: in our sexual past, our thought lives, our marriages and relationships or our words. So where can we find the forgiveness we need? And whether it’s in our thoughts or marriages or words, where can we find the power to live differently?

The Sinner’s Faithful Friend
Throughout the Bible, one of the defining pictures of God’s relationship with his people is that of a husband loving his wife. Except the wife is adulterous. He loves her, but she keeps running off after other lovers. That was true for the people of Israel, but you also know it’s true for you. God loves you, yet sometimes you look elsewhere to other stuff to satisfy you deep down: whether that’s sex, or romance, or relationships, or the desire for power that makes it possible that you’d think about breaking your word. And yet God does not divorce you. He carries on loving you. More than that, Christ came, as the husband for his wayward bride, to woo you back to himself. And he doesn’t walk away from you, he dies for you. He doesn’t cut you off, he is cut off for you. He is the self-sacrificing husband. And whilst lust is about taking, love is about giving and Christ gave himself for you. And at the cross he died for all the sexual and non-sexual sins you and I have committed. He took all our unfaithfulness upon himself, and nailed it to the cross. And it has all been paid for. And it’s there, at the cross, that all of us, adulterers, lustful, promise breakers and liars, divorced, married or single, can all find the forgiveness we need in Christ, and the cleansing that tells us a new start is possible.

And the power for that new start, the power to live differently begins at the cross. As we come in repentance and faith, as we are united with Christ in his death, and filled with his Spirit, so we can count ourselves dead to sin and alive to God. As Paul says in Galatians 5, ‘Those who belong to Christ Jesus have crucified the flesh with its passions and desire’ (Gal 5:24). And what is crucified need have no power over you, because what Jesus calls you to do, he gives you the power to do.

You see, each time here Jesus says, ‘you have heard it said’, he then says, “But I say to you.” And Jesus words are words of life. And as we feed our hearts on his words, and allow his words to form our minds and our hearts, then we find our desires coming into line with his. And as we grow in our understanding of just how faithful a friend he has been to us, who don’t deserve it, so our desire to be faithful to him and to others will grow, to his glory and our good.