Because most people today leave God out of the picture, they take sin lightly. Mainstream Christianity teaches that "all we have to do is believe" and God will take care of the rest. This stems from not really knowing God or His purpose for us!
God created the entire universe—He set in motion, sustains, and controls every power, force and energy. He actively rules His creation. The laws that He set in motion, whether physical or spiritual, determine our well being—or lack of it.
What is sin? Scripture says, "Sin is the transgression of the law" (I John 3:4). Whoever establishes the law is the only one who can then define what sin is. The Bible is clear that God Himself establishes law (Isaiah 33:22) and God only (James 4:12)! Thus, the laws God has set in motion cannot be undone except by Him.
God does not allow us—mere mortal, carnal human beings—to determine what sin is. He has already done that! However, He does allow us to decide whether to sin—and warns us that the penalty of sin is eternal death (Romans 6:23; Matthew 25:46; II Thessalonians 1:9).
Sin is doing what God says is harmful and injurious to oneself and/or others. It deprives a person of God's blessings—peace, happiness, security, abundant and joyful living, as a condition to God's gift of eternal life (Romans 2:13; 6:23; Matthew 19:16-17).
Many people commonly think that God's law has been "done away" or that it was "nailed to the cross" when Christ died. They believe that He came in human form to do away with a horrible set of guidelines that He had given in the first place (James 4:12; Exodus 20:1)! (See I Corinthians 10:4 for the identity of the God of the Old Testament.) These false notions completely fail to take into account the plain words of Jesus Christ:
It is difficult to imagine a society without an enforced law. It is painfully obvious that chaos and anarchy would result—a twisted sort of "survival of the fittest." How, then, can "doing away with law" be the path to peace, joy, and liberty? On the contrary, an accepted standard of conduct is necessary to accomplish the goals of any social group—if its members abide by the rules.
Consider the same scenario on a universal scale. The Creator of mankind has put into place both physical and spiritual laws that reflect His character and way of life. As our creator, God knows how men can live an eternally peaceful, fulfilling, and abundant life—something mankind alone cannot figure out! Because of this fact, God has revealed to humanity—who clearly do not know how to get along (Romans 3:17)—how to love Him (as shown by the first four of the Ten Commandments) and fellow man (the last six commandments). Christ explains in Matthew 22:36-40 that the two Great Commandments encompass everything in "the Law and Prophets." Everything in the Word of God points out the way to have a right relationship with God first—which includes keeping the Sabbath—and with our fellow man.
I John 5:2-3 makes this abundantly clear: "By this we know that we love the children of God, when we love God and keep His commandments. For this is the love of God, that we keep His commandments. And His commandments are not burdensome."
Next: Jesus Christ's Example