"I am the resurrection and the life. The one who believes in me will live, even though they die; and whoever lives by believing in me will never die. Do you believe this?" (John 11:25-26).

I recently shared these words of Jesus with the father of my oldest friend. Chris's father, Joe, was suffering from a brain tumor, and the doctors had given him only weeks left to live.

When I walked in to see Joe, I didn't know if he would want to talk about his approaching death. Joe had always been strong and capable. He had a voice so deep that no matter what he was speaking about, it resounded with confidence and authority, leaving little room for vulnerability.

But as soon as Joe saw me he said, "Hey Vince. Good, I'm glad you're here. I told Chris I wanted to talk to you." Joe went on to tell me that although he had always been confident that God exists in some way, he was finding himself increasingly scared about what comes next.

As we spoke, what became clear to me was that Joe's understanding of the central message of Christianity was that you should try to do more good than bad in your life, and then just hope that in the end your good deeds will outweigh your bad deeds. If they do, something wonderful awaits. But if they don't, you're in trouble. And as Joe reflected back over his life, he recognized that if that was the case, then he had reason to fear.

Never was I so incredibly thankful to be sitting before someone as a Christian. As an atheist, I would have had to say there is no hope beyond the grave. If I adhered to almost any other religion, I would have had to tell Joe that he was basically right, and did have reason to fear what was next.

But as a Christian I was able to explain to Joe that while Christianitydoes say that God wants us to do good, that is not what makes us right with God. I was able to share with him that the message of Christianity is that what makes us right with God is not about anything we do or ever could do, but rather about what Jesus has already done – once, and in full, and for all. I explained that if we trust in Jesus, we no longer need to fear judgment, because when he died Jesus took the judgment for everything we have ever done or will ever do wrong. And we no longer need to fear suffering, or shame, or even death, because Jesus has joined us in all of it, and invited us beyond it.

I explained this at length, and when I asked Joe if this made sense, he responded – in classic New Jersey fashion – "That's a hell of a realization." Emphatically he said it again, and then continued, "Sixty-nine years and I never thought of that. I thought Christianity was one thing, but it was something else entirely." There was an extended pause, and then Joe said, "You know, Vince, you spend your whole life trying to make up for your [mess] ups, but this finally explains how we can deal with guilt."

I asked Joe if he wanted to pray with me to accept this gift from God. He said he did, and with great conviction he thrust out his arm to me. We clasped hands, and we wept, and we prayed, and as we finished praying he exclaimed a loud "Amen."

Joe asked me if my wife Jo knows this great truth about Christianity as well. I said that she does, and he said, "It must be a happy life." And then, after a thoughtful pause, "Now I'm actually looking forward to what's next."

When Joe's family saw him the next day and asked how he was, for the first time in a long time he responded, "Wonderful." The transformation in him was so visible that his family called me immediately and wanted to know every word that I had shared with him.

Life after death, on its own, does not bring hope. Forgiveness brings hope. And I believe, because I was there to see it, that forgiveness, and therefore hope, can be found with a simple heartfelt prayer.

Dr Vince Vitale teaches at Oxford University, is senior tutor at the Oxford Centre for Christian Apologetics, and is a speaker for RZIM. His new book 'Why Suffering? Finding Meaning and Comfort When Life Doesn't Make Sense' (Hachette, 2014), co-authored with world-renowned Christian apologist Ravi Zacharias, is out now.