I think I am a Christian but I’m not really sure. How do I make certain?

This text is from a transcript of a talk by David Gooding, entitled ‘God’s Glorious Plan for Creation’ (2007).

The answer to that varies according to who you are, so to speak, and what your makeup is. How can we be sure? Well there are various Scriptures that tell us how to be sure. I'll quote you this one, because in this question it is important to see exactly what Scripture says. I'm quoting to you now from 1 John 5. This is an argument: not my argument but the argument of Scripture.

If we receive the testimony of men, the testimony of God is greater, for this is the testimony of God that he has borne concerning his Son. Whoever believes in the Son of God has the testimony in himself. Whoever does not believe God has made him a liar, because he has not believed in the testimony that God has borne concerning his Son. And this is the testimony, that God gave us eternal life, and this life is in his Son. Whoever has the Son has life; whoever does not have the Son of God does not have life. (1 John 5:9–12)

'If we receive the testimony of men'; well we do often, don't we? We ring up the airport and we say, 'When is the next plane to Toronto?' and some charming female voice tells us a time. We've never seen the dear lady in our all lives and we know that even such people can make mistakes and be careless, but for practical purposes we believe this voice anyway. We know people can sometimes be untruthful, but we do often receive the testimony of men.

Then, says Scripture, the testimony of God is greater. We should believe him the moment he speaks. Moreover, the testimony of God is not only greater, but he has borne testimony concerning his Son, and who should know about God, if God doesn't? Are you prepared to accept God's testimony about his Son and believe what God says about his Son? And the Scripture says that those who believe have the testimony in themselves, meaning that God, by his Spirit, will confirm it in the heart of those that believe on the Son of God.

But notice the alternative. 'Whoever does not believe God, has made him a liar.' You say, 'That sounds very severe: if I don't believe God, I make him a liar?' But wait a minute, if I came to you after this meeting and said, 'Madam, I've noticed you here several nights and I'm delighted to see you. May I be so forward as to ask what your name is?' and you say, 'I'm Mrs Elizabeth O'Rourke.' Just at that moment, a friend comes up to me and you're still there, listening. He says, 'What is that good lady's name?' and I say, 'Well she says it's Mrs Elizabeth O'Rourke, but I find it a bit difficult to believe.' What a dreadful thing for me to say. You've just told me your name is Elizabeth O'Rourke and I don't believe you, and in front of your face, I tell my friend here that I find it difficult to believe you!

If God says something and I don't believe him, I'm making out that he is not to be trusted. He's a liar. You'll not live in heaven with a God whom you regard as a liar. That's why faith is essential. I must believe God. How could I ever live in his heaven if I don't? The verse says that I would have made God a liar because I have not believed in the testimony that God has borne concerning his Son. What is that testimony? What does God say and what does he demand that I believe? It is this: 'that God gave us eternal life, and this life is in his Son'. Now notice how carefully Scripture is speaking. It doesn't say that 'God will give us'. It says 'he gave us'. As far as God is concerned, he has given this eternal life, and that's that. Where is it to be found? It's in his Son and therefore it follows that he that has the Son, has the life.

Let's suppose that have a €10,000 note, and I've placed it inside this book. So the euros are in the book, and if you believe me and you want it, you'll come and grab the book. If you don't come and grab it, I will say, 'Well he didn't really believe me, or else he doesn't need €10,000!' Suppose you come and take the book and, before you've time to open it to find out where this €10,000 note is, your friend comes up and asks 'Have you got the €10,000?' and you say, 'I don't know.' So you didn't believe me after all, for I said that if you have the book, you have the €10,000. And if you don't believe it, or you're not sure of it, then you've made me a liar.

So one answer to this question—I'm only giving one answer for now, but there are other answers, for in my experience there are all sorts of reasons why people feel uncertain—but let's deal now with this one thing and get that clear. Do you want eternal life?

You say, 'Yes, of course I do.'

God says, 'I've given it, and the life is in my Son. If you have my Son, you have the life.' The question therefore becomes, have you got God's Son, have you received him?

You say, 'I don't know whether I have or not.'

Okay, suppose there came a knock on the door and when you went to the door and opened it, it was Jesus Christ standing there, what would you say? You'd say, 'Come in.' And of course he would, because he's given it as his promise: 'Behold, I stand at the door and knock. If anyone hears my voice and opens the door, I will come in to him and eat with him, and he with me' (Revelation 3:20).

So you have his guarantee that if you say, 'Come in, Lord Jesus, I need you. I've no other Saviour but you, come in, please,' he will come in. 'And if you have my Son,' says God, 'you have the life.'

If you say to God, 'But how will I know?' God will say, 'Because I said so, and if you don't believe, you've made me a liar.' You wouldn't want to do that, I presume. The question comes round, therefore, have you, as best you know how, received God's Son into your heart?

I did as a child. I think I told you the other night. I said the words of a little chorus they used to teach children. 'Come into my heart, Lord Jesus. Come in today. Come in to stay. Come into my heart, Lord Jesus'. He did that and I've lived for over seventy years since then, to prove the reality of it. In spite of all sorts of doubts and fears and psychological issues and the ups and downs of life, I've found him true. God's word is true and if the Lord doesn't come before I die and I go home to glory, I go home on this word. Not on my merit. Not on my works. Not on my attainment. Not on my preaching. I go home to glory on the word of God: 'He who has the Son, has life.' I've no other option. I've no other Saviour. I have God's word. I have eternal life. So may all who will come in true repentance and faith.