I am inclined to take the position that the book of Hebrews falls under the General Epistles rather than the Pauline Epistles for a few reasons, three of which are hereunder considered.
In the words of Paul Enns in his book, The Moody Handbook of Theology, “The Authorship of Hebrews has posed a problem throughout the history of the church and has been vigorously debated without resolve. The author nowhere identifies himself in the book, yet it seems he was known to the readers…”
The authorship of the Epistle to the Hebrews is unknown. While some early Christian writers attributed it to the apostle Paul, this claim is disputed. The Pauline Epistles, on the other hand, are explicitly attributed to Paul as their author. The absence of a clear attribution to Paul in the book of Hebrews is one of the main reasons it is categorized as a General Epistle. Although the highly scholarly and excellent vocabulary seems to support an argument for Apostle Paul, in the face of several other arguments, it is safe to classify the book of Hebrews under the general epistles. As concluded by D.A Carson and Johnson J. Moo in the book, An Introduction to the New Testament
“It is far better to admit our ignorance. We do not know who wrote it; almost certainly, the first readers did”
2. Unspecific Audience:
The intended audience of Hebrews is not specified within the book itself, except that the title states “To the Hebrews” which suggests that it was likely written to Jewish Christians or Jewish converts to Christianity. The Pauline Epistles, on the other hand, were generally addressed to specific churches or individuals, such as the Corinthians, the Galatians, or Timothy. The lack of a specific recipient designation aligns with the style of General Epistles.
3. Distinct Theological Differences
The Epistle to the Hebrews exhibits several emphases on themes like the Christology and High priesthood of Jesus Christ, the superiority of Christ and the New Covenant over the Old Covenant and the Mosaic Law, eschatological themes and emphasis on the age to come. On the other hand, Pauline Epistles, focus more on themes like justification by faith, reconciliation, the role of Christ as the head of the Church.
It is important to note that while there are differences in emphases, there are also significant theological similarities between Hebrews and the Pauline Epistles, such as the themes of faith, the role of Christ’s death and resurrection, and the call to persevere in the Christian life.
Metzger, B. M., & Ehrman, B. D. (2005). The Text of the New Testament: Its Transmission, Corruption, and Restoration. Oxford University Press