It is important to study the Book of Hebrews in the light of all Scripture, and not as an isolated book. Even though the author is not directly named, it is generally believed that Paul was the writer of this great book.
The main message of Hebrews is summarized in chapter 6:1, "...let us go on unto perfection" (spiritual maturity). In chapter 1 we see Christ's superiority over the prophets and the angels, those who delivered God's Word in the old dispensation. As you read the Book of Hebrews, note how often the writer related to the word of the Old Testament. He uses many quotations from the Book of Psalms; yet few of us ever look for Christ in the Psalms.
Chapter 2 continues the argument of chapter 1, that Christ is better than the angels. In chapter 3 we move into the third argument for the superiority of Christ: Christ is better than Moses. Of course, Moses was the great hero of the Jewish nation, and for Paul to prove Christ's superiority over Moses was for him to prove the superiority of the Christian faith over Judaism. Paul's motive here was to prevent the people from going back to Judaism, when Christ offered so much more.
The warning in chapter 3:12 applies not only to the Hebrews, but also to believers today. Unbelief is the one besetting sin of Christians, and this unbelief comes from an evil heart. It is one thing to trust God for salvation, and quite another to surrender our wills and lives to Him for daily guidance and service. Many, many Christians are still wandering in the wilderness of defeat and unbelief. They have been saved out of Egypt, so to speak, but they have never crossed into the Promised Land to claim their inheritance in Christ. Sin in the life of the believer is deceptive. It begins small, but continues to grow until it affects our entire outlook on living. Doubting God in one point can lead to unbelief in many points. Those who doubt and disobey are inviting God's chastisement and possible judgment in this life. Unbelief is a serious thing. For a Christian to live a life of unbelief is to live a defeated life, never knowing the joy of a surrendered life of trust in the Son of God, who gave His life to save us eternally, but who also gives us life more abundantly now.
