In his first book on Matthew’s Gospel, maintaining the Canon of the Church, [Origen] testifies that he knows only four Gospels, writing as follows: “Among the four Gospels, which are the only indisputable ones in the Church of God under heaven, I have learned by tradition that the first was written by Matthew, who was once a publican, but afterwards an apostle of Jesus Christ, and it was prepared for the converts from Judaism, and published in the Hebrew language. The second is by Mark, who composed it according to the instructions of Peter, who in his Catholic epistle acknowledges him as a son, saying, ‘The church that is at Babylon elected together with you, saluteth you, and so doth Marcus, my son.’ And the third by Luke, the Gospel commended by Paul, and composed for Gentile converts. Last of all that by John.”
In the fifth book of his Expositions of John’s Gospel, he speaks thus concerning the epistles of the apostles: “But he who was ‘made sufficient to be a minister of the New Testament, not of the letter, but of the Spirit,’ that is, Paul, who ‘fully preached the Gospel from Jerusalem and round about even unto Illyricum,’ did not write to all the churches which he had instructed and to those to which he wrote he sent but few lines. And Peter, on whom the Church of Christ is built, ‘against which the gates of hell shall not prevail,’ has left one acknowledged epistle; perhaps also a second, but this is doubtful. Why need we speak of him who reclined upon the bosom of Jesus, John, who has left us one Gospel, though he confessed that he might write so many that the world could not contain them? And he wrote also the Apocalypse, but was commanded to keep silence and not to write the words of the seven thunders. He has left also an epistle of very few lines; perhaps also a second and third; but not all consider them genuine, and together they do not contain hundred lines.”
In addition [Origen] makes the following statements in regard to the Epistle to the Hebrews in his Homilies upon it: “That the verbal style of the epistle entitled ‘To the Hebrews,’ is not rude like the language of the apostle, who acknowledged himself ‘rude in speech’ that is, in expression; but that its diction is purer Greek, any one who has the power to discern differences of phraseology will acknowledge. Moreover, that the thoughts of the epistle are admirable, and not inferior to the acknowledged apostolic writings, any one who carefully examines the apostolic text will admit. … If I gave my opinion, I should say that the thoughts are those of the apostle, but the diction and phraseology are those of some one who remembered the apostolic teachings, and wrote down at his leisure what had been said by his teacher. Therefore if any church holds that this epistle is by Paul, let it be commended for this. For not without reason have the ancients handed it down as Paul’s. But who wrote the epistle, in truth, God knows. The statement of some who have gone before us is that Clement, bishop of the Romans, wrote the epistle, and of others that Luke, the author of the Gospel and the Acts, wrote it.” But let this suffice on these matters.”
— Eusebius Pamphilius. Church History VI.XXV. NPNF201.