How to be Sure You are a Christian

The year was 1905. A little known clerk named Albert Einstein, who worked in the Swiss patent office, published a scientific paper. The title of his paper was “On the Electrodynamics of Moving Bodies”, but that paper has since come to be better known as Einstein’s General Theory of Relativity. It was a revolutionary document, produced by one of the greatest minds of all time, and the world hasn’t been the same since.

For two hundred years, through the Enlightenment and the Industrial Revolution, people had gone about their business convinced that there were several certainties about the universe in which we lived. For instance, space and time were constants - they didn’t change; they were always the same. Building on the foundations laid by Galileo and Isaac Newton, scientists inhabited a world of certainty. Matter and motion and energy were predictable - the world of physics was a world of logic and design, just waiting for us to discover the laws by which it worked. You could count on these constants. Until Albert Einstein came along!

Einstein discovered that these things that we had once thought were constants are actually changeable - relative to where you were in the Universe and relative to how fast you were travelling. An astronaut in a space vehicle moving at close to the speed of light would age less quickly than his twin brother left here on earth. Time is relative. It can slow down, it can speed up. And some scientists speculate that it can even go backwards! Einstein showed us that time, for 10,000 years of civilization the ultimate constant in our experience, is not a constant at all.

Historian Paul Johnson, in his book Modern Times, suggests that the modern era began with Einstein’s discovery. He says that the General Theory of Relativity ushered us into an Age of Relativism, not just in physics and science, but in every aspect of life. If scientists couldn’t be sure of things that they once thought were constants, how could anyone be sure of anything? How could we be certain about the meaning of our own existence? How could we be sure what is true? How could we believe that such things as love and justice are constants when scientists were no longer sure about the basic building blocks of the Universe?

So Johnson describes the history of our Twentieth Century as a tragic chronicle of people who are no longer sure of anything anymore. Dictators rule at their own whim. Governments make up their own morality as they go along. Standards of proper behavior in society erode like sand at the seashore. We’ve see the rise of situation ethics, of euthanasia, of abortion. Even something as basic as a person’s sexual identity has come into question. Archie and Edith Bunker yearn for the good old days as they sing…

And you knew who you were then,

Girls were girls and men were men.

Newsday, Feb. 2, 1989 ran a story about a jazz musician named Billy Tipton who died at age 74 and was discovered by the funeral director to have been a woman. Not even his three adopted sons knew the secret. “To us, he’ll always be Dad.” said one of them after hearing the news.

In a world where uncertainty rules, where nobody’s sure of anything, we come to a Bible which says that there are some things that we can be sure of. We can be sure that God is love and that He loves us. We can be sure that Jesus Christ is the Son of God and that he came to this earth to live and die for us. And we can be sure that we can have eternal life through Him.

One of the most important words in the book of 1 John is the word “know”. It appears no less than 41 times in five short chapters. God wants us to know these important things. He wants us to be sure about our relationship with Him. The book of 1 John is a book about certainty.

We’re coming now to the end of the book of 1 John, and John begins to sum up his argument. He has told us how we can know who is a real Christian and who isn’t. (That was as much a problem in his day as it is in ours.) There are lots of counterfeits out there. In John’s day, the counterfeits called themselves Gnostics, which means “people in the know”. They said that you had to know a lot of spiritual information, you had to have mystery knowledge revealed to you in order to be a Christian. They emphasized this idea so much that they implied that it didn’t matter how you lived, so long as you had this knowledge. John said that that was baloney. Christianity isn’t a matter of what you know, it is a matter of who you know. A real Christian knows Jesus Christ.

And it does matter how you live. In fact, how you live proves whether you really know Jesus Christ. If you love other people, it shows that you know God, because God is love. If you don’t love others, it’s because you don’t know God. This kind of evidence in a person’s life demonstrates whether or not he is an authentic Christian.

The Gnostics had some weird ideas about who Jesus Christ was. They said that Jesus was just a man, but that the Christ - the divine side of him - came upon him at his baptism. And it left him before he died, because someone who is divine can’t die. When Jesus was born, he was just an ordinary man, and when he died, he was just an ordinary man, so they said. Now this may sound like a strange idea to you, but let me tell you that there are people who still believe this theory today.

John says that this idea just isn’t so. Jesus was born the Son of God, He lived as the Son of God, He died the Son of God, and He rose again the Son of God. Look at 1 John 5:6…

1 John 5:6 This is the one who came by water and blood—Jesus Christ. He did not come by water only, but by water and blood. And it is the Spirit who testifies, because the Spirit is the truth. For there are three that testify: the Spirit, the water and the blood; and the three are in agreement.

This is a pretty hard passage to understand. What is God saying to us here? What does he mean by the water and the blood? Some people, like Augustine and Calvin, have thought that this referred to the ordinances of the Church - Baptism and the Lord’s Supper. Jesus “comes” to us, and we experience his presence, as we observe these ordinances. Others have thought that the water and the blood refer to the crucifixion, when water and blood poured out of Jesus’ side when it was pierced by the centurion’s spear.

But I think that old Tertullian, one of the early church fathers, had the right answer when he suggested that this counters what the Gnostics were saying about Jesus. The water refers to Jesus’ baptism and the blood refers to Jesus’ death on the cross. What John is saying is that Jesus was the Christ at His baptism, and He was the Christ at His death on the cross. He didn’t start being the Christ at his baptism and stop being the Christ at his death. He comes to us as the Christ, fully the Son of God, through the water and the blood.

And this is important, because if he wasn’t the Son of God hanging up there on the cross, then his death wouldn’t have done us any good at all. If Jesus were only an ordinary man up there, then he could only have died for his own sins, not ours.

So the water of His baptism and the blood of His crucifixion are like witnesses in a court of law that Jesus is the Son of God. But there is another witness in that court: the Holy Spirit. The Holy Spirit is the one who takes those dry objective historical facts about Jesus Christ and makes them live. He’s the one who convinces us that this is true. When a person comes to the point in his life when he is willing to put his trust in these facts about Jesus, it is because the Holy Spirit has been at work testifying to him about the truth of these things.

In a Jewish court of law, it was necessary that a matter be established by the testimony of two or three witnesses. And that testimony had to agree - it couldn’t be contradictory testimony. Remember when Jesus was tried before the Sanhedrin? False witnesses came forward, but Mark tells us that though…

Many testified falsely against him, … their statements did not agree.

Here, we have three who do agree: the water, the blood, (both of which were historical facts about the life of Jesus Christ which John saw with his own eyes), and the Holy Spirit. Now that’s not the only testimony we have about who Jesus is. Back in John 5, in a remarkable passage about this very subject of testimony, Jesus tells us that…

• John the Baptist testified about who Jesus is…

• the miraculous work that Jesus was doing testified about who Jesus is…

• the Scriptures of the Old Testament testified about who Jesus is…

• Moses, the great leader of the Jews, testified about who Jesus is…

• God the Father himself testified about who Jesus is…

And it is about that testimony that John says here in ch. 5…

1 John 5:9-10 We accept man’s testimony, but God’s testimony is greater because it is the testimony of God, which he has given about his Son. Anyone who believes in the Son of God has this testimony in his heart. Anyone who does not believe God has made him out to be a liar, because he has not believed the testimony God has given about his Son.

What is the content of this testimony? What is it that God actually wants us to know about Jesus?

1 John 5:11-12 And this is the testimony: God has given us eternal life, and this life is in his Son. He who has the Son has life; he who does not have the Son of God does not have life.

Eternal life is in the Son of God. It is not in the church. It is not in a creed or a doctrinal statement. It is not in a code of conduct. It is in the Son. It isn’t what you know, it is who you know that determines whether you have eternal life.

Do you know the Son of God, Jesus Christ? Not do you know of him, or about him, but do you really know him? If you do, the Bible says that there is something about which you can be certain. In a world of relativity, and uncertainty, here is something that you can be sure of:

He who has the Son has life; he who does not have the Son of God does not have life.

There are many people today who, if you asked them the question “Do you know that you’ll go to heaven when you die?” would say…

“Well, I hope so.”

“I think so.”

“I’m trying hard to make sure that I do.”

But they’re really not sure. And they’re not sure because they think that eternal life depends on them. They think that they have to live right to get to heaven. They think that they have to somehow earn their way to heaven. And they’re never quite sure if they’ve done enough. Listen, if heaven were something we had to earn by being good, then heaven would be empty, because none of us would make it. Salvation isn’t a do-it-yourself project.

God says that eternal life is a gift. Eternal life is in his Son. If you receive Jesus Christ as your Savior and Lord, then God gives you eternal life. It is as simple as that. No strings attached, no performance clause you have to fulfill. Eternal life is not a contract. It is not an agreement between you and God. It is a gift from Him to you in the person of His Son.

And because it is a gift, we can be sure that we have it. Suppose that somebody were to give you a lovely birthday gift, something that you really liked. But then a few weeks later, they were to come to your house and take it back because they said that you hadn’t really been nice enough to them in the meantime. Was that really a gift? No, it was a performance bond. You do your part and you get to keep it, but fall down on the job and you lose it.

Eternal life is not like that. That is why we can be sure that we have it. Because it is a gift from God. He gave it to us to keep. That is why John wrote…

1 John 5:13 I write these things to you who believe in the name of the Son of God so that you may know that you have eternal life.

It isn’t arrogant or proud to say that you know that you have eternal life in Jesus. In fact, it’s just the opposite! Because eternal life doesn’t depend upon our performance, then we’re not flattering ourselves to say that we have it. Our assurance of our salvation really brings glory to God and His trustworthiness as a faithful gift-giver.

Are you sure that you have eternal life this morning? There’s only one way to be sure. Have Jesus in your life.

1 John 5:11 And this is the testimony: God has given us eternal life, and this life is in his Son. He who has the Son has life

In a world where there seem to be no absolutes, you can hang on to this one certainty: you’ll know where you’re going when you die. Because you’ll know who you’re trusting as you live.

Prayer:

You can receive Jesus right now by simply telling Him, in the quietness of this moment, “Lord, I believe these things. They make sense to me. I believe your testimony about Jesus. I’m ready to take you at your word. I want Jesus to be my Savior and my Lord. I’m not going to pretend anymore that I can live a good enough life to make you want to be with me for all eternity. The only one who can take away my sin and get me into your heaven is your Son Jesus. I’m going to start right now trusting Him for my salvation.”

If you prayed that prayer, I’d like to know about it, so that I can pray for you. And as we continue to pray, I’d like to ask you to slip up your hand and put it down again. The Bible says that when we receive Jesus, we need to confess Him openly. There’s something about letting someone else know what you’ve done that seals the decision for you. Will you tell me what you’ve done?

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You’ve just begun the greatest adventure that anyone can ever have - the adventure of being a child of God. Your problems aren’t over; your little boat is still going to be tossed on life’s sea, but now you’ve got an anchor - the assurance that you have Jesus in your life, and the certainty that you have eternal life in Him.