Lesson: The Forgotten Key to Biblical Evangelism

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“‘I was alive without the law once: but when the commandment came, sin revived’ (Romans 7:9). So it is with the work-righteous and the proud unbelievers. Because they do not know the Law of God, which is directed against them, it is impossible for them to know their sin. Therefore also they are not amenable to instruction. If they would know the Law, they would also know their sin; and sin to which they are now dead would become alive in them.” – Martin Luther

This teaching is critically important. To be properly instructed in how to effectively reach the lost with the gospel, you must begin with the biblical foundation for evangelism. Read this lesson very thoughtfully. Don’t let anything distract you as you discover what Charles Spurgeon called “our ablest auxiliary”—that is, our most powerful weapon.

Have you ever thought, “There must be a key to reaching the lost”? There is—and it’s rusty through lack of use. The Bible does actually call it “the key,” and its purpose is to bring us to Christ, to unlock the Door of the Savior (John 10:9). Not only is it biblical, but it was used throughout church history to unlock the doors of revival. Much of the church today doesn’t even know it exists. The problem is that it was lost around the turn of the twentieth century. Keys have a way of getting lost.

Jesus used it. So did Paul (Romans 3:19,20) and James (James 2:10). Stephen used it when he preached (Acts 7:53). Peter found that it had been used to open the door to release 3,000 imprisoned souls on the Day of Pentecost. Jesus said that the lawyers had “taken away” the key, and had even refused to use it to let people enter into the kingdom of God (Luke 11:52). The Pharisees didn’t take it away; instead, they bent it out of shape so that it wouldn’t do its work (Mark 7:8). Jesus returned it to its true shape, just as the Scriptures prophesied that He would do (Isaiah 42:21). Satan has tried to prejudice the modern church against the key. He has maligned it, misused it, twisted it, and, of course, hidden it—he hates it because of what it does. Perhaps you are wondering what this key is. I will tell you. All I ask is that you set aside your traditions and prejudices and look at what God’s Word says on the subject.

In Acts 28:23 the Bible tells us that Paul sought to persuade his hearers “concerning Jesus, both out of the law of Moses, and out of the prophets.” Here are two effective means of persuading the unsaved “concerning Jesus.”

Let’s first look at how the prophets can help persuade sinners concerning Jesus. Fulfilled prophecy proves the inspiration of Scripture. The predictions of the prophets present a powerful case for the inspiration of the Bible. Any skeptic who reads the prophetic words of Isaiah, Ezekiel, Joel, etc., or the words of Jesus in Matthew 24 cannot help but be challenged that this is no ordinary book.

The other means by which Paul persuaded sinners concerning Jesus was “out of the law of Moses.” The Bible tells us that the Law of Moses is good if it is used lawfully (1 Timothy 1:8). For what purpose was God’s Law designed? The following verses tell us: “The Law is not made for a righteous person, but…for sinners” (1 Timothy 1:9,10). It even lists the sinners for us: the disobedient, the ungodly, murderers, fornicators, homosexuals, kidnappers, liars, etc. The Law was designed primarily as an evangelistic tool. Paul wrote that he “had not known sin, but by the law” (Romans 7:7). The Law of God (the Ten Commandments) is evidently the “key of knowledge” that Jesus mentioned in Luke 11:52. He was speaking to lawyers—those who should have been teaching God’s Law so that sinners would receive the “knowledge of sin,” and thus recognize their need of the Savior.

Prophecy speaks to the intellect of the sinner, while the Law speaks to the conscience. One produces faith in the Word of God; the other brings knowledge of sin in the heart of the sinner. The Law is the God-given “key” to unlock the Door of salvation.

The Bible says in Psalm 19:7, “The law of the LORD is perfect, converting the soul.” Scripture makes it very clear that it is the Law that actually converts the soul. To illustrate the function of God’s Law, let’s look for a moment at civil law. Imagine if I said to you, “I’ve got some good news for you: someone has just paid a $25,000 speeding fine on your behalf.” You’d probably react by saying, “What are you talking about? That’s not good news—it doesn’t make sense. I don’t have a $25,000 speeding fine.” My good news wouldn’t be good news to you; it would seem foolishness. But more than that, it would be offensive to you, because I’m insinuating you’ve broken the law when you don’t think you have.

However, if I put it this way, it may make more sense: “While you were out today, the law clocked you going 55 miles an hour through an area set aside for a blind children’s convention. There were ten clear warning signs stating that fifteen miles an hour was the maximum speed, but you went straight through at 55 miles an hour. What you did was extremely dangerous; there’s a $25,000 fine. The law was about to take its course, when someone you don’t even know stepped in and paid the fine for you. You are very fortunate.”

Can you see that telling you precisely what you’ve done wrong first actually enables the good news to make sense? If I don’t clearly bring understanding that you’ve violated the law, then the good news will seem foolishness and offensive. But once you understand that you’ve broken the law, then that good news will become good news indeed.

In the same way, if I approach an impenitent sinner and say, “Jesus Christ died on the cross for your sins,” it will be foolishness and offensive to him. It will be foolishness because it won’t make sense. The Bible says that “the preaching of the cross is to them that perish foolishness” (1 Corinthians 1:18). And it will be offensive because I’m insinuating he’s a sinner when he doesn’t think he is. As far as he’s concerned, there are a lot of people far worse than him. But if I take the time to follow in the footsteps of Jesus, it may make more sense. If I open up the divine Law, the Ten Commandments, and show the sinner precisely what he’s done wrong—that he has offended God by violating His Law—then when he becomes “convinced of the law as a transgressor” (James 2:9), the good news of the fine being paid will not be foolishness. It will not be offensive. It will be “the power of God unto salvation” (Romans 1:16).

With that in mind, let’s look at some of the functions of God’s Law for humanity. Romans 3:19 says, “Now we know that whatsoever things the law says, it says to them who are under the law that every mouth may be stopped and all the world may become guilty before God.” So one function of God’s Law is to stop the mouth, to keep sinners from justifying themselves by saying, “There are plenty of people worse than me. I’m not a bad person, really.” No, the law stops the mouth of justification and leaves, not just the Jews, but the whole world guilty before God.

In Romans 3:20 we read, “Therefore by the deeds of the law there shall no flesh be justified in his sight: for by the law is the knowledge of sin.” So God’s Law tells us what sin is. First John 3:4 says, “Sin is transgression of the law.” In Galatians 3:24 we learn that God’s Law acts as a schoolmaster to bring us to Jesus Christ that we might be justified through faith in His blood. The Law doesn’t help us; it just leaves us helpless. It doesn’t justify us; it just leaves us guilty before the judgment bar of a holy God.

Charles Spurgeon, called the Prince of Preachers, stated, “I do not believe that any man can preach the gospel who does not preach the Law. The Law is the needle, and you cannot draw the silken thread of the gospel through a man’s heart unless you first send the needle of the Law to make way for it.”