"I do not believe that any man can preach the gospel who does not preach the Law." Then he warns, "Lower the Law and you dim the light by which man perceives his guilt; this is a very serious loss to the sinner rather than a gain; for it lessens the likelihood of his conviction and conversion. I say you have deprived the gospel of its ablest auxiliary [its most powerful weapon] when you have set aside the Law. You have taken away from it the schoolmaster that is to bring men to Christ . . . They will never accept grace till they tremble before a just and holy Law. Therefore the Law serves a most necessary purpose, and it must not be removed from its place."

"The Law cuts into the core of the evil, it reveals the seat of the malady, and informs us that the leprosy lies deep within."

"They must be slain by the law before they can be made alive by the gospel."

"Ask Paul why [the Law] was given. Here is his answer, 'That every mouth may be stopped, and all the world may become guilty before God' (Romans 3:19). The Law stops every man's mouth. I can always tell a man who is near the kingdom of God; his mouth is stopped. This, then, is why God gives us the Law—to show us ourselves in our true colors."

"The law can only chase a man to Calvary, no further."

“It is a great mistake to give a man who has not been convicted of sin certain passages that were never meant for him. The Law is what he needs … Do not offer the consolation of the gospel until he sees and knows he is guilty before God. We must give enough of the Law to take away all self-righteousness. I pity the man who preaches only one side of the truth, always the gospel and never the Law.” EB - Jos 1:7

"A gospel which merely says, 'Come to Jesus,' and offers Him as a friend, and offers a marvelous new life, without convincing of sin, is not New Testament evangelism. (The essence of evangelism is to start by preaching the Law; and it is because the Law has not been preached that we have had so much superficial evangelism.) True evangelism... must always start by preaching the law."

"The trouble with people who are not seeking for a Savior, and for salvation, is that they do not understand the nature of sin. It is the peculiar function of the Law to bring such an understanding to a man's mind and conscience. That is why great evangelical preachers 300 years ago in the time of the puritans, and 200 years ago in the time of Whitefield and others, always engaged in what they called a preliminary law work."

"The only way we can know whether we are sinning is by knowing His Moral Law."

"They are already under a sentence of condemnation to hell. They do not only justly deserve to be cast down thither, but the sentence of the law of God, that eternal and immutable rule of righteousness that God has fixed between him and mankind, is gone out against them, and stands against them; so that they are bound over already to hell. John iii. 18. 'He that believeth not is condemned already.' So that every unconverted man properly belongs to hell; that is his place; from thence he is, John viii. 23. 'Ye are from beneath.' And thither be is bound; it is the place that justice, and God's word, and the sentence of his unchangeable law assign to him."

The German Priest who in the 16th Century broke with the Roman Catholic church and founded the Lutheran Church, said, “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 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.” EB-Num 7

"Satan, the god of all dissension stirs up daily new sects. And last of all which of all others I should never have foreseen or once suspected, he has raised up a sect such as teach that men should not be terrified by the law, but gently exhorted by the preaching of the grace of Christ."

"The first duty of the Gospel preacher is to declare God's Law and show the nature of sin."

"...we would not see nor realize it (what a distressing and horrible fall in which we lie), if it were not for the Law, and we would have to remain forever lost, if we were not again helped out of it through Christ. Therefore the Law and the Gospel are given to the end that we may learn to know both how guilty we are and to what we should again return."

In a sermon published way back in 1537, Martin Luther spoke of the Law being used as a schoolmaster the bring sinners to Christ. Listen to his words of warning: "This now is the Christian teaching and preaching, which God be praised, we know and possess, and it is not necessary at present to develop it further, but only to offer the admonition that it be maintained in Christendom with all diligence. For Satan has attacked it hard and strong from the beginning until the present, and gladly would he completely extinguish it and tread it underfoot."

When preachers in pulpits have no respect for God’s Law, they preach a gospel devoid of reference to it. But God save us from a message that heals the hurt slightly, saying,, “peace, peace, when there is no peace” (Jeremiah 8:11-12). The preaching of our day too often leaves out the necessity of the Law and the reality of Judgement Day and in this way reaps a harvest of professed conversions. These folks refrain from the vices that once decimated their lives. Therefore, they find a measure of healing. No longer is their marriage in jeopardy; there has been an instigation of biblical principles. Friendship and vocation flourish because there is a new understanding of the importance of being trustworthy, loving and showing respect for others. However, if there is no understanding of the nature of sin and the need for biblical repentance , these “converts” are still hell-bound. If they haven’t been born of God, it doesn’t matter how much they have been slightly healed or from which pulpit they have been assured that they have peace with God. EB-Jer 6:13-14

False Prophets, whether during the time of Zephaniah, or the Pharisees in Jesus’ day, or the false prophets of our day, all do “violence to the Law.” They show contempt for the Law, refusing to preach it despite the example of Jesus (see Luke 10:25-26, 18:18-20) and despite the many other verses that speak of the Law’s function, to bring sinners to the Saviour. EB-Zep 3:4

The covenant of the Law was given that we might fear God. Those who preach the gospel with no reference to God’s Law will reap “converts” who have no reverence for God. The end of them is seen in Matthew 7:21-23. They continue in “iniquity” (lawlessness) despite doing wonderful works in His name. The genuine convert will have the law of truth in his mouth. He will magnify God’s Law and make it honourable (see Isaiah 42:21) He has named the name of Christ and departed from iniquity. It (iniquity) is not found in his lips, and he turns many away from iniquity because his preaching makes continual reference to the Law that sinners have violated. Jesus rebuked the lawyers, those who should have been preaching God’s Law to bring knowledge of sin to Israel. He said, “You have taken away the key of knowledge” (Luke 11:52). It is the key of the Law that leads to the door of the Saviour. It is a schoolmaster to bring us to Christ (Galatians 3:24). EB-Mal 2:5-8

The preaching of the Law without retribution will not be effective in winning souls for Christ. It has been well said that God’s Law without consequences is nothing but good advice. The world will agree with “Thou shalt not kill.” That makes sense. They will smile at “Thou shall not commit adultery.” They know it destroys families. They will give assent to “Thou shall not bear false witness.” They know it breaks friendships. The Ten Commandments certainly are good advice. However, when you preach the Law with the message that God “will judge the world in righteousness (as Paul preached in Athens, see Acts 17:22-31), your listeners will be provoked to say, “we will hear you again about this matter” (Acts 17:32). And sinners will be soundly saved. EB-Mal 3:5

This is what God’s Law does to the receptive sinner. He sees his own desperately wicked heart revealed under the brilliant light of the Ten Commandments. And he suddenly sees sin as being “exceedingly sinful” (Romans 7:13). He has a straight edge so that he can understand how crooked he is. It halts the mouth of justification. That’s what God’s Law does, it “stops every mouth and leaves the whole world guilty before God” (Romans 3:19). EB-Job 40:4
Matthew 19:17-22: Here is the Master evangelist showing us how to deal with a proud self-righteous person – a typical sinner. This is noticeably different from the approach of modern evangelism. When the man asked how he could obtain eternal life, Jesus did not ask, “Would you like to have assurance that if you died tonight you would go straight to heaven ? You can that confidence right now simply by acknowledging that you have sinned against God, and by trusting in the finished work of Calvary’s cross. Would you like me to lead you in a prayer right now so that you can have assurance?”
Instead Jesus pointed him to the Law so that he could recognise his sin. Biblical evangelism is always “Law to the proud, grace to the humble” John Newton said, “My grand point in preaching is to break the hard heart and to heal the broken one.”
This young man is a prime example of an unregenerate person. He had no understanding of the word “good.” Jesus reproved him, then gently gave him five horizontal Commandments – those dealing with his fellow man. When the man revealed his self righteousness, Jesus showed him that in his vertical relationship with God he had transgressed the first of the Ten Commandments. God wasn’t foremost in his life. The rich young man loved his money, and the scriptures make it clear that we cannot serve God and mammon (money). The Law brought him “the knowledge of sin.”
In light of the way most Christians share the gospel, Jesus failed because he didn’t get a “decision”. However Heaven doesn’t rejoice over “decisions”. It reserves it’s rejoicing for repentance, and there can be no repentance without a God given knowledge of sin – and that, according to Scripture, can come only by the Law. (Roman 7:7) EB-Mat 19:17-22