The Epistle to the Hebrews in Fausset's Bible Dictionary

Canonicity. - Clement of Rome (1st century A.D.) refers to it oftener than any other canonical New Testament book, adopting its words as on a level with the rest of the New Testament. As the writer of this epistle claims authority Clement virtually sanctions it, and this in the apostolic age. Westcott (Canon, 22) observes, it seems transfused into Clement's mind. Justin Martyr quotes its authority for applying the titles "apostle" and "angel" to the Son of God. Clement of Alexandria refers it to Paul, on the authority of Pantaenus of Alexandria (in the middle of the second century) saying that as Jesus is called the "apostle" to the Hebrew, Paul does not in it call himself so, being apostle to the Gentiles; also that Paul prudently omitted his name at the beginning, because the Hebrew were prejudiced against him; that it was originally written in Hebrew for the Hebrew, and that Luke translated it into Greek for the Greeks, whence the style resembles that of Acts. He however quotes the Greek epistle as Paul's, so also Origen; but in his Homilies he regards the style as more Grecian than Paul's but the thoughts as his. "The ancients who handed down the tradition of its Pauline authorship must have had good reason for doing so, though God alone knows the certainty who was the actual writer," i.e. probably the transcriber or else interpreter of Paul's thoughts. The Peshito old Syriac version has it. Tertullian in the beginning of the third century, in the African church, ascribes it to Barnabas. Irenaeus in Eusebius quotes it. About the same time Caius the presbyter of Rome mentions only 13 epistles of Paul, whereas if epistle to Hebrew were included there would be 14. The Canon fragment of Muratori omits it, in the beginning of the third century. frontCANON.) The Latin church did not recognize it as Paul's for a long time subsequently. So Victorinus, Novatian of Rome, and Cyprian of Carthage. But in the fourth century Hilary of Poitiers (A.D. 368), Lucifer of Cagliari (A.D. 371), Ambrose of Milan (A.D. 397), and other Latins quote it as Paul's; the fifth council of Carthage (A.D. 419) formally recognizes it among his 14 epistles...

Link: https://bible-history.com/faussets/H/Hebrews,+the+epistle+to+the/