Most of today's Christians seem to think that we know longer must deal with the law of God. This concept of thinking can be refuted by Jesus' statement in Matthew 5:17 which says that He came to fulfill the law and not to destroy it. The Greek word fulfill {play-ro'-o} in Matthew 5:17 means among other things to: complete, consummate, render perfect, carry through to the end, accomplish, bring to realization, perform, execute, accomplish, or bring to pass. We also, must fulfill the law but it does not come on our own abilities or we would have no need of the Savior. We are to fulfill the law of God by walking after the Spirit (Romans 8:4). Christians are not to walk by the law but rather according to the law. This walk is accomplished by Jesus Christ who brought us grace and truth, just as Moses brought the spiritually dead the Law.
Therefore it is important to have knowledge of the entire Word of God including the law. It provides a standard which leads us to Jesus Christ (Gal. 3:24). This concept is also valid for a New Testament Christian who realizes ones inability to uphold a lifestyle according to the Word of God, void of Jesus Christ. When we try to uphold the Word of God by ourselves, Christ has become no good to us and we are no longer under the grace which Jesus brought but under the law (Gal. 5:4).
Jesus knew exactly what to tell the lawyer who asked him which commandment in the law was the greatest. Jesus said in Matthew 22:37-40 "Thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind. This is the first and great commandment. And the second [is] like unto it, Thou shalt love thy neighbor as thyself. On these two commandments hang all the law and the prophets." Paul later would say that all the law is fulfilled in one word, 'love' (Gal. 5:14). If you place others before self, as Jesus Christ did, you will walk according to the law. The key is to walk in the fruit of God's Spirit, which no law can be against. This means a moment by moment dependence on Jesus Christ to manifest Himself through the Holy Spirit in order to uphold the perfect, holy law of God. Because if you be led by the Spirit, ye are not under the law, but you are able to walk according to the law (Gal. 5:18).
The law consist mainly of the first five books of the Old Testament,
called the Pentateuch. Within this law are contained what we
comonly know as the Ten Commandments.
Thou shalt not have any other gods before me
Thou shalt not take the name of the LORD thy God in vain
Remember the Sabbath day, to keep it holy
Hounour thy father and thy mother
Thou shalt not kill
Thou shalt not commit adultery
Thou shalt not steal
Thou shalt not bear false witness against thy neighbour
Thou shalt not covet thy neighbours property