A powerful story of forgiveness launches a BBC Radio 4 Lent series on Sunday themed around the idea of hospitality.

Presented by Rev Dr Krish Kandiah, it focuses on the seven last words of Jesus from the cross.

He said: 'I have recently discovered something astonishing about the last seven statements Jesus made before he died. They may appear unrelated at first sight, but they are intrinsically linked to one another because all of them relate to the practice of hospitality.'

The series, he said, would feature 'people who have found hope in tragedy, forgiveness from shame, and welcome from isolation and now want to pass on the help they have received themselves on to others, and perhaps help to escape their loneliness and find a passion for hospitality'.

The first in the series, to be broadcast on Sunday March 10, features Martin and Rachel Riddall, whose son Sam was killed in a car accident nine years ago. They reflect movingly on his life and death, and on how they have struggled with forgiveness.

As they had begun to worry that he had not returned home from a Friday night youth club, Martin received a call saying Sam had been in an accident and that he should 'prepare for the worst'. 'When I got there Sam was already in an ambulance, he'd been run over by a car that had been going twice the speed of the speed limit being driven by a lady who was high on various types of recreational drugs and who hadn't slept apparently for about 48 hours,' he says. They were told at the hospital that he had died.

On the day of his death he had had a conversation about dying and heaven with his mother.

Martin – a military chaplain – says: 'On the Sunday we went to church, and the support we got from the gathered family or body of Christ was really, really helpful. Another thing that was really helpful was that because Sam had asked those questions, we were aware of his own faith that he held for himself, so for us there was no guessing or hoping about where he might be.

'If we were not already prepared, if we hadn't got the faith that we'd got, and if that faith hadn't been practised and trained and taught, then we would have had to at that time try and work out how on earth do we allow our faith to get us through. But because we'd already got it in us, it came out, it was there already.'

Asked about how she coped with forgiving the woman responsible, Rachel – who is on the leadership team of Woodlands Church, Bristol – says: 'It is really hard. We decided as a couple and as a family that we would pursue forgiveness. That even though at times we didn't feel like we wanted to forgive her we would ask God to help us to be able to forgive her.

'Now we're nine years later and there are days when I feel like, "Yeah, I've forgiven you for what you've done." And there are other days when it feels really hard.

'I remember reading a quote even before Sam died, and I was preaching on forgiveness, it was Nelson Mandela, and he said "Resentment is like drinking poison and hoping it will kill your enemy". But it actually just screws you up and it's a slow death for you.

'I remember preaching that and it was so real to me, and I thought I don't want to be that person that is bitter and twisted and can;t forgive somebody when I know I've been forgiven by God. So I guess that's the position that we've chosen to take.'

The interview with Martin and Rachel Riddall will be included in Radio 4's Sunday Worship programme on March 10 at 8.10 am. Rev Dr Krish Kandiah will be the preacher.