What is the Law of God for Christians?
The Law is not the Ten Commandments or all the other commandments. The Law is the complete Bible from Genesis 1:1 to Revelation 22:21. All Christians should be careful to keep the moral laws in the Bible. That does not mean we are to struggle and wear ourselves out trying to keep the sacrificial and ceremonial commandments found in the Old Testament; they were all fulfilled by: Jesus Christ.
Jesus did not come to abolish the Law, but to fulfill it (Matthew 5.17) so we do not have to. He lived the perfect life keeping the Ten Commandments, the Torah, the Law and all of the sacrificial, ceremonial and moral laws for us. We do not have to keep any of them to be saved or to keep our salvation. We only need to keep the moral laws to abide in Jesus (John 15.4-5), and to walk, to be led by and to live by the Holy Spirit (Galatians 5.16, 18, 25).
Remember the admonition of Paul:
Therefore do not let anyone judge you in eating or drinking or in respect of a feast or of a new moon or of Sabbaths – which are a shadow of things to come; but the body is of Christ. (Colossians 2.16-17)
No one can tell other Christians that they must keep the Sabbath, the Old Testament feasts or the dietary laws. Everyone who does that is sinning and they will have loss of reward for doing that. No Christian needs to keep the Sabbath, the feasts or the dietary laws to abide in Christ. When we think we have to keep them we stop abiding in Him. Instead we are walking and living in the flesh. Some cults teach that salvation depends on keeping the ceremonial laws (Sabbath/feast keeping) and the dietary laws. Those who believe that have believed a false gospel ("another gospel"). According to Paul they are anathema (Galatians 1.6, 9). God does not need us to cleanse our sins. In fact it is a grave insult to Him to think that we can add anything to His finished work on the cross.
Remember, just as Jesus Christ died for us by shedding His blood to cleanse us of our sins (Romans 5.8; Revelation 1.5), He also lived for us. As noted previously He lived the perfect life for us so we do not have to live it. His vicarious life and death are totally sufficient for us. We do not have to die for our own sins and neither do we have to live a perfect life keeping all of the ceremonial and moral laws to be saved or to abide in Christ. If we did none of us could be saved and none of us could abide in Christ. We would all fall short and end-up in hell.
Everyone has to live a perfect life to enter heaven. No one can live in the presence of God and without being perfect and without sin. Since no one who has ever lived has lived a perfect and sinless life everyone would go to hell. Right? Wrong!
Those who trust in Jesus the Messiah by accepting His atonement on the cross for them have all of their sins (past, present, future) cleansed. They become sinless so they are essentially accepting His perfect life of keeping the Law, including the Sabbath, feasts, ceremonial laws, dietary laws and moral laws. His perfect life is given to those who trust in Him making them perfect.
It is because believers have all their sins cleansed by the blood of Christ and given His perfect life that they can enter heaven and live with God through all eternity. Because believers are given the perfect life of Jesus the Messiah they do not have to keep the Law! They do not have to keep the Sabbath and the feasts. They do not have to keep the ceremonial, dietary and moral laws! Jesus Christ kept all of them for every believer!
Out of obedience and love for the Lord all believers should pray without ceasing, be in the Scriptures daily, fellowship with the brethren and share the gospel as the HOLY SPIRIT leads. As they do those things they will keep the moral laws, but they will not always keep the Sabbath, the feasts or the dietary and ceremonial laws. There will be times when believers will not be able to keep them because they will be doing the will of God when He may want His children to help the needy on the Sabbath or a feast day instead of keeping the Sabbath or the feast.
Remember, Jesus lived the perfect life for all believers. They do not have to live it. No matter how hard we try it is impossible. God desires "faithfulness and not sacrifice, and the knowledge of Elohim more than burnt offerings" (Hosea 6.6). This means that He wants His children to do His will more than legalistically keeping the Law, Sabbath, feasts, etc. It is far more important to know God than to be legalistic and keep the Law, which Jesus kept for us. He kept the Law so you do not have to keep it! All He wants is for believers to do His will, which sometimes means not keeping the Sabbath or a feast day.
One last thing: Even though there will be numerous times when it will be the will of God for His children to not keep the Sabbath, a feast or dietary law so they can do His will, He will never have them break a moral law to do His will. He will never ask one of His children to break a moral law; such as not lying, stealing, or committing adultery to do His will. There is a great difference between the moral laws and the ceremonial laws (Sabbath/feast keeping and dietary regulations).
Not keeping ceremonial laws does not harm other people. It is a matter between each believer and God. But not keeping the moral laws always harms others. This is why it can be the will of God for His children to not keep the Sabbath, feasts, dietary laws, etc., if it is His will that they should help someone in need. Yet it will never be His will for His children to break a moral law and harm someone.
We must keep in mind that no one can keep any of the moral laws in their own power. It is only by the power of the Holy Spirit that we can keep any moral law. Keeping the ceremonial laws does not enable us to keep the moral laws. It is the act of daily abiding in Jesus and being led by, living by and walking in the Holy Spirit that enables us to keep the moral laws. The way we do that is to pray always (1 Thessalonians 5.17), be in the Word every day reading, studying, memorizing and meditating on it, fellowshipping with the brethren (Acts 2.42, 46-47; Hebrews 3.13; Hebrews 10.24-25), sharing the gospel with the lost as the Holy Spirit leads and make disciples (Deuteronomy 4.9-10; 6.5-7; 11.18-19; 32.4; Psalm 78.3-7;Matthew 28.19-20).
God wants His children to abide in Christ by daily being in prayer and in the Word, and by fellowshipping and sharing the gospel as often as possible. He does not want His children to spend more time keeping the Sabbath, the feasts and dietary laws than they do praying, studying the Word, or being in fellowship and sharing the gospel.