It’s a bit of a challenge this parable, isn’t it? That ending – Jesus telling us that if we don’t behave then God will torture us. That’s a tough thing to hear on a Sunday morning.

Especially since the point of this parable is to tell us to forgive people. It seems, well, let’s say it seems rather contradictory for God to be telling us to forgive one another – and then not forgiving us. What’s that about?

And it’s not just that part that’s hard – it’s also this –Jesus seems to be saying that we have to forgive other people in order to be forgiven. Which sounds worryingly like a transaction. If I forgive someone for some petty grievance, then God will forgive me for some petty sin. But the logic of that is terrible – if I forgive lots of people then I will be forgiven a lot – which means I can sin a lot.

Surely not. Surely not what we are intended to take away from this Gospel. We’re going to have to dig a little deeper.

And my starting point is that this is a story. Jesus is a master storyteller – over and over we see him come up with stories to help us understand something about God. And this particular story is one which is full of hyperbole, wild exaggeration, great overblown fabrications which make a point – make several points actually. And the first point he makes is to tell Peter to think big.

How often should I forgive someone, Peter asks – as many as seven times? And Jesus – well, you can practically hear his eye roll as he says to Peter “Seven? Not seven – seventy seven!” In fact – little aside here – in Greek, the language the Gospel was written in, the phrase used could mean 77 – but it actually says seventy times seven, 490. The point is that Peter is thinking way, way too small. He thinks he’s being generous suggesting that he forgives someone seven times – in fact, Jesus tells him to up his game, to be much, much more generous than that.

And Jesus’s dramatic overstatements continue in the story he tells to help Peter understand. So this first servant, he owes the king 10,000 talents. Ten thousand – that’s going to be a lot, right? We might not know how much a talent is, but we can be pretty sure that this is a big sum of money, because 10,000 of anything is going to be quite a lot of cash.

Well, I did the maths. Let’s start with the second slave. He owes the first one 100 denarii. Even if we know nothing of biblical currency, we can tell from the story that this is a lot less money. In fact, we know that historically the going rate for a day’s work was one denarius. So actually, 100 denarii is going to be a significant sum of money – 100 days’ work is a fair bit. I worked out that if the slave were paid the London Living Wage, 100 denarii would amount to over £8,000 by today’s standards. So not insignificant.

But how much is 10,000 talents? Well – are you ready? - a talent was apparently 6,000 denarii. Six thousand. Six thousand days’ work for one talent - and this slave owed the king 10,000 of them.

Works out at £5 billion. Five billion. Our low-paid London Living Wage slave would have to work for 2,300 lifetimes to pay that back. It’s a staggeringly large amount of money, a ridiculous amount of money. Basically Jesus just said the slave owes the king eleventy billion dollars – and the king let him off.

Kind of puts things into perspective, doesn’t it? Bearing in mind that this is a parable about God’s forgiveness of us. God is prepared to cancel a huge, huge amount of debt, debt beyond our wildest imaginings, debt it would take us forever to rack up and which we would literally never be able to pay off. God will forgive.

But we must also forgive. That’s the bottom line. But it’s not the bottom line because this is a transaction, a quid pro quo. No, it is, I think, simply because it is impossible for us to be forgiven if we don’t forgive. Forgiving is what enables us to be forgiven.

Tom Wright, the former Bishop of Durham and one of the most important New Testament scholar of the last 100 years, describes forgiveness as being like the air in your lungs. There is, he says, “only room to inhale the next lungful when you’ve breathed out the previous one”. I think this is a brilliant metaphor. Forgiveness, like breath, is life giving – but you have to keep doing it. Seven times isn’t enough. Even seventy times seven isn’t enough – you have to keep at it, forgiving all the time.

If you don’t, if you hold onto that lungful of breath, if, as Tom Wright says, “you insist on withholding [forgiveness], refusing to give someone else the kiss of life they may desperately need, you won’t be able to take any more in yourself”.

And I think that’s true. We have to forgive in order to be forgiven because forgiveness only works if we ask for it, confident that it will be given. That’s the problem Joseph’s brothers have in the first reading – they don’t think they will be forgiven. Not unreasonably – they did after all sell their brother into slavery… And like Peter, they simply can’t imagine forgiveness big enough.

So the point of Jesus’s parable of forgiveness is not the threat of torture at the end – which suddenly starts to look like another piece of ridiculous exaggeration. No, the point of the parable is in fact the certainty of forgiveness, the ridiculous generosity of the God who will forgive us eleventy billion times.

The forgiveness is there for us. It is there for everyone who understands that forgiveness is the air that we breathe, who understands that letting go, releasing the anger, the pain, the regret, the bitterness of refusing to forgive - who understands that forgiving other people is quite simply how we heal. How we are forgiven ourselves.

There is no end to God’s forgiveness. All we have to do is to understand that we too can forgive. All we have to do is let go of our injury. All we have to do is ask God, confident that God’s forgiveness is infinite.

All we have to do is breathe out.