Are there any clues as to who might have authored the book of Hebrews?
The author of Hebrews is unknown. As early as 255 AD, church leaders concluded the author of the book was unknown. Some speculate it was Paul, and from 400-1600 AD the Roman church declared the letter to be the Epistle of Paul to the Hebrews. The writer has a firm grasp of the OT pictures of Christ, and he has an in-depth understanding of the Jewish culture, sacrificial system, law, prophets, OT scripture, etc. Even the closing of the letter sounds a little like Paul and mentions Timothy, a protege of Paul.
But these similarities do not prove Paul was the author, and other evidence suggests Paul didn’t write the letter. For example, a large number of Greek words used in this letter are found nowhere else in scripture (including in Paul’s letters), and many of Paul’s characteristic phrases are missing, including kathos ge grap tai (As it is written…). The letter is also missing Paul’s typical introduction, prayers for the readers, benediction and thanks.
So if this letter were written by Paul, then he radically altered his usual vocabulary and style, which seems unlikely. Therefore, it’s unlikely Paul was the author.
A clue to authorship is found in Chapter 2, where the writer refers to himself as one who never personally encountered Christ himself (2:3). Apostles were men appointed by the Lord personally, and all scripture was authored directly or indirectly by an apostle, yet this author says he received the Gospel handed down from others and not from the Lord personally. If the author himself never encountered the Lord, then he could not be an apostle, which also argues strongly against Paul as the author.
Nevertheless, since the early church fathers accepted this letter as scripture, they must have had reason to believe the content was authored under apostolic authority, if not by an apostle personally. Therefore, the author may have been the traveling companion of an apostle, much like Luke who traveled with Paul and Mark who shadowed Peter. In such a case, the content originated from an apostle’s teaching and was recorded by someone who accompanied that apostle. Perhaps the author was someone who shadowed Paul, which would account for the letter’s similarities with Pauline theology yet its departure from Pauline style.
In the end, we should respect the Lord’s decision to obscure the author by not naming anyone, since we can’t be sure in any case.