Notice, in His familiar words in the Sermon on the Mount, His teaching about the commandments of God: "Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill" (Matthew 5:17 Matthew 5:17Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfill.
American King James Version×). Jesus spoke plainly. God's law is not abolished, and, according to Christ's own words, anyone who teaches otherwise directly contradicts Him and is in serious trouble (Matthew 5:18-19 Matthew 5:18-19  For truly I say to you, Till heaven and earth pass, one stroke or one pronunciation mark shall in no wise pass from the law, till all be fulfilled.  Whoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whoever shall do and teach them, the same shall be called great in the kingdom of heaven.
American King James Version×).
Some people assume and teach that we do not need to keep God's law because Jesus "fulfilled" it. But they fundamentally misunderstand Christ's clear words. The word translated fulfill in this passage means "to make full, to fill to the full" (Vine's Complete Expository Dictionary of Old and New Testament Words, 1985, "Fill"). The same word is used of filling up nets with fish (Matthew 13:48 Matthew 13:48Which, when it was full, they drew to shore, and sat down, and gathered the good into vessels, but cast the bad away.
American King James Version×). In the same way that a fisherman fills his nets with fish, Jesus perfectly "filled up" the law of God. He perfectly kept the Ten Commandments, including the spiritual intent of God's laws and how we should apply them.
How did Jesus expand on the law, showing its fuller and deeper spiritual intent? Notice one example in Matthew 5:27-28 Matthew 5:27-28  You have heard that it was said by them of old time, You shall not commit adultery:
 But I say to you, That whoever looks on a woman to lust after her has committed adultery with her already in his heart.
American King James Version×: "You have heard that it was said to those of old, 'You shall not commit adultery.' But I say to you that whoever looks at a woman to lust for her has already committed adultery with her in his heart."
The immoral act of committing adultery is defined as a sin by the Seventh Commandment (Exodus 20:14 Exodus 20:14You shall not commit adultery.
American King James Version×). Yet the literal wording of that commandment—the letter of that law (2 Corinthians 3:5-6 2 Corinthians 3:5-6  Not that we are sufficient of ourselves to think any thing as of ourselves; but our sufficiency is of God;  Who also has made us able ministers of the new testament; not of the letter, but of the spirit: for the letter kills, but the spirit gives life.
American King James Version×)—does not fully reflect God's intent. Jesus showed that the spirit of the law—its spiritual intent—is much broader than the letter and encompasses even our thoughts toward others. Lustful thoughts, He taught, are mental, emotional and spiritual adultery and are contrary to a basic principle of His will—loving our neighbor as we love ourselves (Matthew 22:39 Matthew 22:39And the second is like to it, You shall love your neighbor as yourself.
American King James Version×).
Similarly, Christ expanded the intent of the Sixth Commandment, which prohibits murder (Exodus 20:13 Exodus 20:13You shall not kill.
American King James Version×). "You have heard that it was said to those of ancient times, 'You shall not murder'; and 'whoever murders shall be liable to judgment.' But I say to you that if you are angry with a brother or sister, you will be liable to judgment; and if you insult a brother or sister, you will be liable to the council; and if you say, 'You fool,' you will be liable to the hell of fire" (Matthew 5:21-22 Matthew 5:21-22  You have heard that it was said of them of old time, You shall not kill; and whoever shall kill shall be in danger of the judgment:  But I say to you, That whoever is angry with his brother without a cause shall be in danger of the judgment: and whoever shall say to his brother, Raca, shall be in danger of the council: but whoever shall say, You fool, shall be in danger of hell fire.
American King James Version×, New Revised Standard Version). Jesus explained that uncontrolled or unjustified anger can break the spirit of the Sixth Commandment.
He continued: "Again you have heard that it was said to those of old, 'You shall not swear falsely, but shall perform your oaths to the Lord.' But I say to you, do not swear at all . . . But let your 'Yes' be 'Yes,' and your 'No,' 'No.' For whatever is more than these is from the evil one" (Matthew 5:33-37 Matthew 5:33-37  Again, you have heard that it has been said by them of old time, You shall not forswear yourself, but shall perform to the Lord your oaths:
 But I say to you, Swear not at all; neither by heaven; for it is God's throne:
 Nor by the earth; for it is his footstool: neither by Jerusalem; for it is the city of the great King.
 Neither shall you swear by your head, because you can not make one hair white or black.
 But let your communication be, Yes, yes; No, no: for whatever is more than these comes of evil.
American King James Version×).
Jesus' teaching about oaths illustrates another aspect of applying the spirit of the law rather than just the letter of such biblical commands. In this example the spiritual principle underlying the law demands that those who serve God should be truthful in everything they say. They should not have to be required to swear an oath before their words can be regarded as honest and factual. Therefore the commandment telling us not to "bear false witness against your neighbor" (Exodus 20:16 Exodus 20:16You shall not bear false witness against your neighbor.
American King James Version×) should mean far more to us than only being required to tell the truth if we are under an oath. Jesus made the New Testament application of this command even more demanding by saying, "Do not swear at all."
With the help of His Spirit, God enables us to discern that the intent of a law may extend far beyond the letter—the exact wording—originally written in the five books of the law, the first five books of the Bible. God expects us to look at specific problems that the written laws address and discern how we should apply the intended principles of those laws in reference to the spirit or intent of all of God's Word as magnified by Christ and His apostles.
This requires a wisdom and spiritual balance that we can attain only if we are guided by God's Spirit. Those who do not have the Spirit of God simply do not have this discernment. Rather, they naturally tend to be "hostile" to God's laws (Romans 8:7 Romans 8:7Because the carnal mind is enmity against God: for it is not subject to the law of God, neither indeed can be.
American King James Version×, NIV) and perceive them as "foolishness" (1 Corinthians 2:14 1 Corinthians 2:14But the natural man receives not the things of the Spirit of God: for they are foolishness to him: neither can he know them, because they are spiritually discerned.
American King James Version×). They do not see them as the wisdom of God that needs to be properly discerned and "correctly handled" (2 Timothy 2:15 2 Timothy 2:15Study to show yourself approved to God, a workman that needs not to be ashamed, rightly dividing the word of truth.
American King James Version×, NIV).
God will help us, through His Spirit, to begin to discern how to apply the principles contained in the Scriptures in this manner—to discern and comprehend the proper application of those Scriptures. This means that the standards for our conduct will be even higher than those expressed in the literal words—in the letter of the laws—recorded for us in the Old Testament.
Jesus illustrates this with two other examples. First, He explains: "For I say to you, that unless your righteousness exceeds the righteousness of the scribes and Pharisees [who prided themselves in obeying the letter of the law] you will by no means enter the kingdom of heaven" (Matthew 5:20 Matthew 5:20For I say to you, That except your righteousness shall exceed the righteousness of the scribes and Pharisees, you shall in no case enter into the kingdom of heaven.
American King James Version×; compare Luke 18:11 Luke 18:11The Pharisee stood and prayed thus with himself, God, I thank you, that I am not as other men are, extortionists, unjust, adulterers, or even as this publican.
American King James Version×).
He also taught: "So likewise you, when you have done all those things which you are commanded, say, 'We are unprofitable servants. We have done what was our duty to do'" (Luke 17:10 Luke 17:10So likewise you, when you shall have done all those things which are commanded you, say, We are unprofitable servants: we have done that which was our duty to do.
American King James Version×). Our righteousness has to exceed the letter of the law. We become profitable servants of God only if we begin to discern and apply to the way we obey Him the primary principles (such as faith, hope, love, justice, good judgment and mercy) on which all of the Word of God is based.
God gives us His Spirit so we can properly discern and apply the spirit and intent of the Holy Scriptures. (To better understand the spiritual foundation and intent of God's laws, be sure to request your free copy of the booklet The Ten Commandments.)