Some of my favorite passages come from the book of Hebrews. Each time we read it, we find new applications. That's because God's Word is alive and active and never comes back void, but accomplishes just what He sent it to do.
For the word of God is living and active. Sharper than any double-edged sword, it penetrates even to dividing soul and spirit, joints and marrow; it judges the thoughts and attitudes of the heart. HEB 4:12
The following is a brief summary from GotQuestionsMinistries.org
The Book of Hebrews addresses three separate groups: believers in Christ, unbelievers who had knowledge of and an intellectual acceptance of the facts of Christ, and unbelievers who were attracted to Christ, but who rejected Him ultimately. It’s important to understand which group is being addressed in which passage. To fail to do so can cause us to draw conclusions inconsistent with the rest of Scripture.
The writer of Hebrews continually makes mention of the superiority of Christ in both His personage and in His ministering work. In the writings of the Old Testament, we understand the rituals and ceremonies of Judaism symbolically pointed to the coming of Messiah. In other words, the rites of Judaism were but shadows of things to come. Hebrews tells us that Christ Jesus is better than anything mere religion has to offer. All the pomp and circumstance of religion pales in comparison to the person, work, and ministry of Christ Jesus. It is the superiority of our Lord Jesus, then, that remains the theme of this eloquently written letter.
Connections: Perhaps nowhere in the New Testament does the Old Testament come into focus more than in the Book of Hebrews, which has as its foundation the Levitical priesthood. The writer to the Hebrews constantly compares the inadequacies of the Old Testament sacrificial system to the perfection and completion in Christ. Where the Old Covenant required continual sacrifices and a once-a-year atonement for sin offered by a human priest, the New Covenant provides a once-for-all sacrifice through Christ (Hebrews 10:10) and direct access to the throne of God for all who are in Him.
Practical Application: Rich in foundational Christian doctrine, the Epistle to the Hebrews also gives us encouraging examples of God's "faith heroes" who persevered in spite of great difficulties and adverse circumstances (Hebrews 11). These members of God's Hall of Faith provide overwhelming evidence as to the unconditional surety and absolute reliability of God. Likewise, we can maintain perfect confidence in God's rich promises, regardless of our circumstances, by meditating upon the rock-solid faithfulness of God's workings in the lives of His Old Testament saints.
The writer of Hebrews gives ample encouragement to believers, but there are five solemn warnings we must heed. There is the danger of neglect (Hebrews 2:1-4), the danger of unbelief (Hebrews 3:7–4:13), the danger of spiritual immaturity (Hebrews 5:11–6:20), the danger of failing to endure (Hebrews 10:26-39), and the inherent danger of refusing God (Hebrews 12:25-29). And so we find in this crowning masterpiece a great wealth of doctrine, a refreshing spring of encouragement, and a source of sound, practical warnings against slothfulness in our Christian walk. But there is still more, for in Hebrews we find a magnificently rendered portrait of our Lord Jesus Christ—the Author and Finisher of our great salvation (Hebrews 12:2).