“The Moral Law” (A Dr. O Special) – Exodus 20:1-17

Preached by Roger McCay
10 October 2021
Sermon Passage: Exodus 20:1-17
Link to Audio Version
Link to Dr. O’s Preaching of the Sermon

This sermon was written by Dr. Robert J. Ostenson, and he originally preached it on 25 January 1976, at Trinity Presbyterian Church, Montgomery, AL. It is part one of a series of eleven sermons on the Ten Commandments. As a tribute to Dr. O, and due to the enduring value of these sermons, Dr. Roger McCay transcribed it from the original sermon tapes, preaching it on 10 October 2021, at Monroeville Presbyterian Church, Monroeville, AL. This series is wonderful and relevant to every generation. A pastor could take these sermons and preach them 100 or 1000 years from now and still speak truth to the lives of the hearers.

“The Moral Law”

This morning’s sermon is on the 10 Commandments. A study of this kind, I think, is timely, because the 10 Commandments have something to say to a deteriorating human society. The 10 Commandments have something to say to that person who is yet outside of Jesus Christ. And the 10 Commandments have something to say to the Christian. Now, it’s also important that we study the 10 Commandments because there is a great deal of confusion, even among Christians, as to the place and relationship of the 10 Commandments to the gospel of grace. There are many people today who are like the Galatians of old who predicate salvation not simply by grace through faith but faith plus the works of the law. There are other groups of believers who believe that because all pertaining to salvation is of grace, the 10 Commandments have no place in God’s economy for the Christian. Now, as to answer this last thing, to start a foundation for our study of the Commandments, we have chosen the subject before us this morning. And that is the relationship of the law and the gospel.

Now let me warn you right at the outset this morning, you are going to have to put on your thinking caps. I hate to say that, but you have to. I know a lot of people come to church on Sunday morning, and they’ve been busy and used their brains all week long. And they come, and they say, “Preacher, leave me alone.” This sermon is not designed to appeal to your aesthetic sense. This is designed for you to deal with the very spiritual cement and steel and timbers of your faith, which is necessary for committed Christian living. And it’s important for us, this morning, to put down a solid foundation, in order to build our study of the 10 Commandments. So, you’ve gotta put on your thinking caps. And I warn you, you’ll probably go away from this sanctuary this morning and say, “Uhhh!” But we’ve got to put down a foundation. And you’ve got to use your head a little bit this morning, rather than just your emotions.

First of all, let’s define terms. What do we mean by the moral law? We mean the expression of God’s eternal moral will—what the eternally righteous Creator and Lord of this universe has revealed concerning his desire and requirement of his creatures. It’s the divine declaration of God’s holy will, which is binding upon all men at all times and in all places.

Having said that, we immediately come to face the fact that there are certain basic facts that we either have to admit or we have to deny. And the first basic fact is this: that the God of creation, the Lord of this universe, is an absolutely perfect and righteous and just and holy God; and that this perfect God has created a moral universe in which he has revealed a moral law; and conformity to his moral law is right and nonconformity is wrong. In other words, God has created a universe in which there are moral absolutes. And there is such a thing as absolute right and absolute wrong.

Now, we shall not take the time to go into all the Scriptures, this morning, that declare this. But I don’t know whether you realize this or not, but this is really what’s at the root of the problem in our society today—this very thing. Paul says in Romans, “There is no fear of God before [men’s] eyes.”[1] And because men no longer believe that God is a moral God, and that he’s created a moral universe, and he’s revealed a moral law, men have come to the place that they think they can do anything that they want to and are not accountable to a holy God. So, this is the first basic fact that we have to face, that God is a perfectly righteous, just, and holy God, who has revealed a moral law and created a moral universe, in which there are some absolutes.

Our own confession of faith, chapter two, says:

There is but one only, living, and true God, who is infinite in being and perfection, a most pure spirit, invisible, without body, parts, or passions; immutable, immense, eternal, incomprehensible, almighty, most wise, most holy, most free, most absolute; working all things according to the counsel of His own immutable and most righteous will, for His own glory; most loving, gracious, merciful, long-suffering, abundant in goodness and truth, forgiving iniquity, [and] transgression, and sin; the rewarder of them that diligently seek Him; and withal, most just, and terrible in His judgments, hating all sin, and who will by no means clear the guilty.[2]

Now, we say all this simply to point out the sharp contrast that exists between the revelation in God’s Word of a perfect moral God who has revealed to men a moral law. This in sharp contrast to a society today which has disregarded this God, who says there is no morality in God, there’s no morality in this universe, and have set about to establish a system of human morality and ethics on a fluid foundation of relativism. And this is what has been taught in our colleges and our universities and our seminaries, in the past few decades. Situational ethics, moral relativism, and man’s only problem is if he gets caught. Everything is relative. So, this is in sharp contrast. This is why I say we either have to admit or deny certain basic facts. And this is the first one. Is there a moral God and a moral law to which men are accountable?

The second basic fact is that this God created man. And he so created him, so that he would be a moral being who is responsible to this moral God. And he created him in such a way that man was responsible for living in obedience and conformity to God’s revealed moral law. And yet at the same time, man was given the capability of obeying or disobeying God’s law. In other words, man was created as a responsible moral agent with a capacity for either obeying or disobeying this revealed moral law of God.

Now we know when we turn to the third chapter of the book of Genesis, we have there the story of the fall of Adam and Eve and how they rebelled against the revealed moral will of God. They did their own will. And, as a consequence, something happened to Adam and Eve. They lost the fellowship and communion that they had with their creator. But furthermore, their intellect became darkened to spiritual matters. Their will became perverted to self-will rather than the desire to do God’s will. And their emotions became deadened, so that they were no longer lovers of God, but they were lovers of themselves. Adam transgressed. He failed to conform. He failed to measure up and keep the revealed will of God. Remember our catechism definition? “Sin is any want of conformity unto or transgression of the will of God.”[3]

Alright, because this had happened to Adam and Eve, all of this was passed on to their posterity. And man, by nature, now became alienated and separated from his creator. And he was not subject to the will of God, neither indeed could be. He lost his capacity to obey and conform to the revealed will of God. Now, there is something that should be pointed out, that this moral law (which had been written on the table of Adam’s heart and conscience) was not obliterated. It was obscured. It was not clear like it had been before the fall. But there were still vestiges of it on his conscience. This is what Paul is talking about in Romans 2, when he talks about the condemnation on both Jew and Gentile, and says this: “For when the Gentiles, which have not the law, do by nature the things contained in the law, these, having not the law, are a law unto themselves: Which show the work of the law written on their hearts, their conscience also bearing witness, and their thoughts the mean while accusing or else excusing one another.”

You go to the heart of the African jungle or the Brazilian jungle today, and still among some pagan tribes you will find sacrificial altars dripping with blood. Why? Because even the pagan has that innate consciousness that he is alienated from a supreme being and something must be done to bring about reconciliation between himself and this sovereign power.

This is what Paul’s talking about. And although the moral law of God was not obliterated from the conscience and heart of man, it was obscured, dimmed. But it’s still there. It has always been wrong to commit adultery. It has always been wrong to steal. It has always been wrong to covet. And this was written upon man at the creation. The moral law of God upon his conscience and upon his heart.

Now, when God called for himself a nation to make it the vehicle for bringing the Messiah and salvation to the world, he called Moses up onto the top of Mount Sinai. And there he republished the law in written form and put it on two tables of stone—what we know as the 10 Commandments. Along with this he gave Moses the ceremonial and the sacrificial and the political laws for the ruling of Israel. But keep this very clearly in mind. When God gave Moses the 10 Commandments on Mount Sinai, he wasn’t revealing the moral law for the first time. He was simply republishing the moral law, which had been written, originally, upon the heart and conscience of Adam and Eve. And that’s why I say, from the beginning of creation, it’s always been wrong to murder and these other things.

Now, the next point that needs to be made right here is that in the republishing of the law, as it was given to Moses, in the Mosaic revelation, God was not giving a system for the sinner to procure salvation by a system of works righteousness. It was not given to Israel as a means of justification or salvation. And we should keep that clearly in mind. The object of the giving of the Mosaic Law was not for the purpose of giving life but for guiding life. The law has no power to pardon. The law has no power to cover sin. The law has no power to reclaim the sinner. And this is where Israel made a mistake. The Israelites thought that by trying to keep the moral law of God or their own interpretation of the law, they could thereby procure salvation and acceptance with God. And consequently they became self-righteous and legalistic and in bondage to the law. They completely ignored the truth that man in and of and by himself does not have the capacity to keep the moral law of God perfectly.

We read in James 2:10: “For whosoever shall keep the whole law, and yet offend in one point, he is guilty of all.” In other words, to be declared righteous by God by the keeping of the law would necessitate that you and I would have to keep the 10 Commandments perfectly 24 hours around the clock all the days of our life. We couldn’t mess up one single time. If we were to be justified by the keeping of God’s moral law, we would have to live a perfect life. We couldn’t break one of God’s 10 Commandments one time—from the time we are born until the day that we die. Now, I can’t speak for you dear friends, but I can sure speak for myself. Remember, Jesus said that the 10 Commandments could be summed up in the two great commandments: “Thou shall love the Lord thy God will all thy heart with all thy mind with all thy soul and all thy strength…. And thou shall love thy neighbor as thyself.”[4] Now, let me ask you. Have you loved God in this manner—24-hours around the clock every day of your life? And have you loved your neighbor as yourself (never back biting; never talked about him; never gossiped about him; never tried to get even with him) every day of your life? 24 hours? No, the 10 Commandments were never given as a system of righteousness whereby we could obtain salvation, by the keeping of the law. The Scripture says, “For all have sinned and come short of the glory of God.”[5] “There is none righteous, no, not one.”[6]

Now, in view of this, the next most natural question to ask is, “What then is the purpose of the 10 Commandments?” Why did God give men his moral law? Theologians have come up with three basic reasons for the giving of the law.

The first is what we might call the political purpose of the law. And this has its application to all of human society. And here, its main function is to restrain sin; to keep down unrighteousness; that God has revealed to this unregenerate world that there is a moral God and there is a moral law to which the sinner is accountable. And in this way, human society is restrained from sin and evil breaking out completely. And it serves to remind this world of sinful men that they are morally accountable before a holy God who hates and punishes sin.

Now, incidentally, this ties into what Paul talks about in Second Thessalonians, chapter 2, where he talks about conditions that are going to prevail in our world before the second coming of Christ; when all of the rebellion, all the kicking off of restraint, is going to come in its consummation; when there is going to be a complete breakdown of law and order within human society, which is going to come to its consummation, in the appearance of the Antichrist.[7] Now, reflect upon this in light of our society today: the rebellion against moral law; the rebellion against God’s word; the rebellion against God himself; man doing his own thing completely, doing his own will rather than the revealed will of God.

The second purpose of the law is what they call pedagogic, or the schoolmaster function of the law. We read in Galatians 3:24, “Wherefore the law was our schoolmaster to bring us unto Christ, that we might be justified by faith.” The purpose of this part of the law was to escort unregenerate men to the place where they realized that they were sinners and that they had to look someplace else for help and for hope outside of themselves. And in this respect, the law becomes a means of grace, because it gives us a true picture of sin. And it has unmasked man as a rebel against his creator, and a man in need of salvation.

Such passages as Romans 3:19, “Now we know that what things soever the law saith, it saith to them who are under the law: that every mouth may be stopped, and all the world may become guilty before God. 20 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.” Romans 7:7: “What shall we say then? Is the law sin? God forbid. Nay, I had not known sin, but by the law: for I had not known lust, except the law had said, Thou shalt not covet.”

To simplify this, this simply means this purpose of the law was to hedge men in and convince and convict him of his need of a savior. By holding the perfect moral standard of God before him, man in convicted and convinced that he cannot measure up to God’s just demands, and he has to look to something or someone outside of himself to gain acceptance and reconciliation with God. This purpose of the law was to crowd man to Christ and convict him of his need of a savior. This was also the function of the sacrificial law, as God gave it to Israel. As foregleamed shadows typed, pointing man to the need of atonement by a blood sacrifice. And this was culminated and fulfilled in the person of Christ and his work at the cross. The ceremonial law has been abrogated; it has been fulfilled, in the person and work of the Lord Jesus Christ. It no longer has any meaning.

But what about the purpose of the moral law of God for you and me right here? Now, we have said that the law is not binding in the way of salvation. In fact, the New Testament says that we are dead to the law. We have been redeemed from under the law. No man can be saved by trying to keep the 10 Commandments. “By the works of the law shall no flesh be justified in his sight.”[8]

But you see, the Christian need not have great fear of the law. The law need not be a terror to him. Why? Because the Lord Jesus Christ has fulfilled all the just demands of the law for the believer. The Son of God came into this world. First of all, he perfectly fulfilled the just demands of the law. Jesus is the only person who ever lived on this earth who was without sin. Jesus is the only man who ever kept the law of God perfectly. This is what the Bible means when it says he “fulfilled all righteousness.”[9] He did what the first Adam failed to do, thus procuring eternal life. But more than that, the Lord Jesus Christ went up on the cross, and he paid the penalty for the broken law. Remember when God said to Adam, “In the day that thou [sinneth], thou shalt surely die.”[10] “The wages of sin is death.”[11] “The soul that sinneth, it shall die.”[12] And God had decreed that the penalty for the failure to conform, the penalty for transgressing the moral law of God was death. Jesus Christ was born to die. He came into this world and went up on to the cross. And he died the death that you and I should have died. As our substitute, he paid the penalty. He took our sins on his own body on the tree. And he gave up his life unto death, as an atoning sacrifice for your sin and mine. And, in doing this, he satisfied divine justice, fulfilling the just demands of the broken law and made it possible for you and for me to experience the forgiveness of our sins, to be reconciled with our creator from whom we were alienated. And this is why it says “Jesus Christ bore our curse in his own body on the tree.”[13] He took our place. He was our substitute. He was the Lamb of God that had come to take away the sin of the world. And this is why the Christian need not be in terror of the moral law of God. Its just demands have been met in the person of the Savior. Christ did it for us.

But this is not true of the unregenerate. The moral law still stands above the unregenerate, as God’s revelation of his perfect standard. And man is still accountable for his failure to measure up to the just demands of God’s law.

This is what we mean then by the schoolmaster function of the law of God—to hedge man in and convince him of his own need and point him to the Lord Jesus Christ, as the only savior from sin and its punishment.

The third and final aspect of the law of God for you and for me. Alright, if we’re saved by grace through faith, if we’re justified by faith in Christ alone, then what purpose do the 10 Commandments have for you and for me? Does it mean, then, that we don’t have to worry about the 10 Commandments? … the 10 Commandments no longer have any application to you and to me because we are justified by grace through faith? And the answer to that question is “No,” which brings us to the didacting (or teaching) function of the law, which simply means this: The 10 Commandments will forever be the divine standard for conduct. They are still the revelation of God’s eternal moral will for perfect conduct.

Now keep it in mind, don’t get it mixed up here. We are not saved; we do not earn salvation; we do not gain salvation, by trying to keep the 10 Commandments. We are saved by grace through faith. But the 10 Commandments serve as a standard of perfect obedience held before the Christian for godly Christian conduct. And the Christian is called to godly Christian conduct in sanctification, and this conduct is epitomized in the 10 Commandments. It serves as a rule of moral good and evil for the believers walk and manner of life. It’s a standard that we always aim at; we don’t achieve it. We don’t achieve it. It’s always there before us. It’s like Paul says, “Not as though I have perfect … I have attained … but I press on.”[14] But we do not reduce that moral standard, and this is vital. At the beginning of the sermon this morning, I said there are groups of Christians that say that because we are saved by grace through faith, “I’ve got my eternal insurance policy paid for. Now I can do anything I please. I can live like I wish.” Not so. Not so. Because the 10 Commandments are still God’s divine revelation of the perfect moral standard to which we aim and to which we conform our lives, constantly.

Remember, Jesus said that the 10 Commandments could be summed up in the two great commandments—love to God and love to our neighbor. And the commandments declare how this kind of love ought to behave, how our love toward God ought to behave, how our love toward other men ought to behave: that you will not covet, that you will not steal, that you will not bear false witness, that you will not commit adultery. And the 10 Commandments still remain for the Christian God’s revelation of how this love ought to behave.

Now, when you turn to Jeremiah, chapter 31, you read about another covenant that God said he’d make:

“After those days, saith the Lord, I will put my law in their inward parts, And write it in their hearts; And will be their God, And they shall be my people. And they shall teach no more every man his neighbor, and every man his brother, saying, Know the Lord: For they shall all know me, From the least of them unto the greatest of them, saith the Lord: For I will forgive their iniquity, And I will remember their sin no more.”[15]

What does this mean? In this prophetic utterance, God was declaring the day would come when he would give man a new spiritual heart, a new spiritual heart that would love and want to obey God’s moral law. Jesus Christ brought this about, made this possible, through his death and resurrection, and through the sending of the Holy Spirit to apply that redemption to the hearts and minds of believers. And, as a consequence, because the Holy Spirit now has come and regenerated the believer and given him a new spiritual heart, the Christian now has the capacity and an indwelling power to enable him now to more and more conform to the standard of the divine lawgiver. You see, a person has to be personally related to the divine lawgiver in order to obey. Obedience is within the family of God, and the Bible says that you and I have received adoption as sons. The forgiven Christian is not a lawless Christian. Let me say that again. The forgiven Christian is not a lawless Christian. Through the indwelling presence and divine power of the Holy Spirit living within him, his desire now becomes to be more and more conformed to the likeness of his lawgiver. This is what Paul talks about when he talks about sanctification in the New Testament. “For this is the will of God, even your sanctification,”[16] to be more and more conformed to the likeness of Jesus Christ.

The law of God is perfect. It is immutable. It lasts forever. And it is still filled with significance for our day. It says to an unregenerate society, “Look how far astray you have gone from the moral God of this creation.” It says to the unregenerate heart, “You’re a sinner. You don’t measure up. You break the law of God. You need a Savior.” And it says to the Christian; it says to the believer, “Here is my perfect moral standard. Now, by God’s grace and the power of the Holy Spirit, you begin to live in such a way that you more and more conform to this perfect moral standard.” In the word of the song of Psalm 19, “The law of the Lord is perfect, converting the soul: The testimony of the Lord is sure, making wise the simple.”[17]

And it’s to this law, Lord willing, that we’re going to give our attention [as an occasional series interspersed over the next year or so]. [This Law] has something to say to every one of us.

May we pray:

Our Father and our God, we thank thee this morning that we live in a universe where thou has revealed that thou art a moral God. Thou has revealed thy eternal moral will, in the 10 Commandments: that this is a schoolmaster to hedge us in, to convince us of our failure and our sin, and point us to a Savior; that it also serves as a magistrate to this whole unbelieving world, to convince them of the fact that they live in a moral universe, responsible to a moral God; and Father, that it speaks to us, that there is a standard for our lives, epitomized in the person of Jesus Christ himself, who kept the law of God perfectly. And so, Father, we pray that thou helps us, by thy Holy Spirit, to understand these things aright. And then, Father, that it might be a blessing in our own hearts and lives, that we will be impressed with what Jesus Christ has really done for us in his salvation and his redemption that he procured at the cross. We ask in Christ’s name, Amen.


[1] From Rom. 3:18. All passages are from the KJV.

[2] The Westminster Confession of Faith, II. 1.

[3] The Westminster Shorter Catechism, Question 14.

[4] Mark 12:30-31

[5] Romans 3:23

[6] Romans 3:10

[7] For Dr. O, the Man of Lawlessness (2 Thess. 2) equals the Antichrist (1 John 2). Dr. O hints, here, as to his theological understanding of 2 Thess. 2, 1 John 2, and Rev. 20, concerning the time at the end of the millennium before Christ’s final return, when Satan is to be released “for a little while” with the increased apostasy and persecution.

[8] Romans 3:20

[9] Matthew 3:15

[10] From Gen. 2:17

[11] Romans 6:23

[12] Ezekiel 18:20

[13] From 1 Peter 2:24

[14] From Philippians 3:12

[15] Jeremiah 31:33-34.

[16] 1 Thessalonians 4:3

[17] Psalm 19:7.