Was the Epistle to the Hebrews written by the Apostle Paul?

The Epistle to the Hebrews appears in the New Testament after the thirteen Pauline letters and before the seven catholic (or general) epistles. For the most part, the early Church attributed the epistle to St. Paul, but the western Church had its reservations. Tertullian attributed the epistle to Barnabas, while both Gaius of Rome and St. Hippolytus excluded Hebrews from the letters of Paul, the latter attributing it to St. Clement of Rome. By the fourth century, both East and West had thoroughly accepted Pauline authorship for the epistle.

The author of Hebrews is anonymous and the recipients of the letter are also anonymous. The only biographical reference in the letter is to "our brother Timothy" in Heb 13:23. It is believed that both the author and the recipients are in all probability Jewish converts to Christianity. To judge from its contents, the letter was addressed to a Christian community whose faith was faltering because of strong Jewish influences in the area (probably Antioch).  The community was doubting whether Jesus could really be the Messiah for whom they were waiting because they believed the Messiah prophesied in the Old Testament was to come as a militant king and destroy the enemies of his people. To fortify Christian beliefs, the author describes the perfect priesthood of Christ (although of a different sort than the traditional Levitical priests), who, unlike the Jewish high priest, offered but one sacrifice as God’s own Son, thereby redeeming all of mankind once and for all. The office of the Jewish high priest, by contrast, was filled by a temporary appointee whose imperfect sacrifice had to be repeated over and over. His role as a king is yet to come, and so those who follow him should be patient and not be surprised that they suffer for now. The author concludes that Christianity is consequently superior to Judaism. The extended treatment of Moses, Aaron, and the Levitical priest, along with its extensive Old Testament quotations, also indicate a Jewish audience. The location where the epistle was written is also unknown, although the author probably wrote it in Italy ("Those from Italy send you greetings", Hebrews 13:24), although it could've been written in a place where Christians from Italy were living and the letter was being sent to Rome. 

Just as the authorship of Hebrews is unknown, so is the date. Because of its use in the First Epistle of Clement, which is dated around 95 AD by some scholars, most agree that the date must be prior to 95 AD. However, the real debate centers around whether or not it was written before the destruction of the Temple of Jerusalem in 70 AD. Because the letter warns Christians against the temptation of returning to the ancient Levitical form of worship, it would seem to have been written before the temple's destruction. After all, if the purpose of the letter is to show the end of the Mosaic law, the destruction of the temple would make a stronger argument and surely would have been mentioned in the letter. Hebrews also warns more severely against apostasy than any other book in the New Testament. If the recipients were in Rome and the temptation to deny the faith was exceptional at the time the letter was written, the plausible setting would be during the persecution of Roman Christians under Nero in 64 AD. These facts combine to create a window of time for the dating of Hebrews, set sometime during or after the burning of Rome in 64 AD but before the destruction of Jerusalem in 70 AD. 

Internal examination of the text does show that it is in many ways different from the rest of Paul’s writings. For example, it does not carry the usual greeting and introduction, the overall vocabulary and style is very sophisticated and different from Paul's other letters, and the fact that it does not quote Scripture in the way Paul typically does. Furthermore, the Koine Greek of the letter is in many ways the best in the New Testament. Its doctrine is thoroughly Pauline, but the way it is written makes it difficult to attribute its direct authorship to Paul.  Some scholars think it may have been written by Barnabas, Paul’s missionary companion. This would explain the letter’s resemblance to Paul’s theology. Furthermore, Barnabas was a Levite and would have been acquainted with the levitical system, a major theme in Hebrews. Others have suggested Apollos, an Alexandrian Jewish Christian mentioned in the New Testament, noted for his eloquence (Acts 18:24-28), because of the way that the letter quotes the Old Testament and its beautiful style and language. The attribution to Apollos is not recent, but in fact traces back to Martin Luther on the grounds that the author says the message “was confirmed to us by those who heard.” There are several reasons why Apollos could have hypothetically written Hebrews and none to argue against it, except that the early tradition of the Church does not support it. In any event, this is a secondary question that has nothing to do with matters of faith.

However, I believe there is a multitude of reasons to believe that the Apostle Paul wrote the Epistle to the Hebrews.

1.  Paul had a great deal of knowledge about the Old Testament

Paul, unlike any of the seventy apostles, was a Pharisee since his youth, taught by Gamaliel the Elder, the leading rabbinical authority at the time, in the law and the entire Old Testament. In Acts 23:6, Paul is written as saying: "Brothers, I am a Pharisee, a son of Pharisees." In Acts 22:2-5, he says to the Jews in Aramaic: “I am a Jew, born in Tarsus in Cilicia, but brought up in this city at the feet of Gamaliel, educated strictly according to our ancestral law, being zealous for God, just as all of you are today." Unlike many of the other apostles, Paul not only knew the Christian but also the Jewish way of thinking since his earliest youth. 

2. The stylistic difference was due to Paul's adaptation to the knowledge of the addressees

In the fourth century, Eusebius of Caesarea wrote that Paul omitted his name in the epistle because he, the Apostle to the Gentiles, was writing to the Jews. Had the Jews known it was written by Paul, it likely would've been dismissed. However, why was the Epistle to the Hebrews written in a different style and used different vocabulary? Clement of Alexandria recounts a tradition that says the epistle was said to be originally written in the language of the Jews (either Aramaic or Hebrew) but translated into Greek by St. Luke, the author of the Gospel bearing his name and the Acts of the Apostles. However, for the purpose of this argument, I believe the reason there is a stylistic difference is simply to adapt to the needs of a more specific audience, the Jewish Christians, who were being persecuted and pressured to go back to Judaism. For the Gentile Christians, Paul used a very simple language to not overwhelm them. They needed spiritual milk because they were spiritual babies. Paul wrote to the Corinthian community in the First Epistle to the Corinthians: "I fed you with milk, not solid food, for you were not ready for solid food. Even now you are still not ready." (3:2). For children, simple words must be used. But among the Jews, he could speak quite differently and argue in a different way, for they needed not only milk but also solid food. Paul even criticized the Hebrews for the fact that some still needed milk even though they should have been teachers long ago (Heb 5:12-14). Throughout the epistle, Paul quotes the Old Testament extensively and describes Christ's fulfillment of it. The average Gentile Christian knew very little of a Melchizedek, but a Jew would have known exactly what was meant and can understand Paul's reasoning (Heb 7). Furthermore, some similarities in wordings to some of the Pauline epistles have been noted. The epistle contains Paul's classic closing greeting, "Grace be with all of you" as he stated explicitly in 2 Thessalonians 3:17–18 and Titus 3:15 and as implied in 1 Corinthians 16:21–24 and Colossians 4:18. This closing greeting is included at the end of each of Paul's letters.

3. Parallels between Hebrews and Paul’s other writings

Many of the thoughts in the epistle are similar to those found in Paul’s writings:

Hebrews	Paul's writings
Hebrews 1:3 "He [Jesus] is the reflection of God’s glory and the exact imprint of God’s very being, and he sustains all things by his powerful word."	Colossians 1:15 – 17 "He [Jesus] is the image of the invisible God ... For in him all things in heaven and on earth were created ... and in him all things hold together.
Hebrews 2:4 "while God added his testimony by signs and wonders and various miracles, and by gifts of the Holy Spirit, distributed according to his will."	1 Corinthians 12:11 "All these are activated by one and the same Spirit, who allots to each one individually just as the Spirit chooses."
Hebrews 2:14 "Since, therefore, the children share flesh and blood, he himself likewise shared the same things [humanity], so that through death he might destroy the one who has the power of death, that is, the devil"	Philippians 2:7 – 8 "Being born in human likeness and being found in human form, he humbled himself and became obedient to the point of death—even death on a cross."
Hebrews 8:6 “But Jesus has now obtained a more excellent ministry, and to that degree he is the mediator of a better covenant, which has been enacted through better promises.”	2 Corinthians 3:6 “who has made us competent to be ministers of a new covenant, not of letter but of spirit; for the letter kills, but the Spirit gives life.”
Hebrews 10:14 “For by a single offering he has perfected for all time those who are sanctified."	Romans 5:9; 12:1 “now that we have been justified by his blood"; “present your bodies as a living sacrifice, holy and acceptable to God.”

Regardless of who wrote the epistle, I think one thing is significant. Of all of the possible candidates—Luke, Barnabas, Apollos, and Clement of Rome—they all have one thing in common: they had contact with or were disciples of St. Paul. St. Paul was, in some way or another, the source of the Epistle to the Hebrews. Whether he wrote the work himself or it was written by an author close to Paul or based on his teachings, Hebrews and Paul are connected. Regardless of how the Letter to the Hebrews is produced, its primary author is the Holy Spirit. In this aspect, Father Andrew Louth gives a very compelling argument that the whole New Testament is apostolic, but not always strictly written by the apostles, because we believe that the books of the New Testament are canonized by the Church, based on apostolic spirit and doctrine. Although his paragraph is describing the Gospel According to Matthew, I believe it can equally apply to the entire New Testament canon:

"It seems to me that modern biblical scholarship has only shown us the stark truth that Christianity finds its beginning in faith in the resurrection: faith, not in the sense of a paradoxical commitment that reposes on nothing, but faith in the sense of trust in the community of faith that is the Church. If that is true, then it seems to me that it does not matter too much whether Matthew, for instance, was an apostle: the Gospel was attributed to him because the Church felt it was fundamentally apostolic, and in some way Matthaean, maybe because some of the stories concerned him. It is, if you like, rather the case that it was because the witness of that Gospel was felt to be genuinely apostolic that the Church was happy about its attribution to Matthew, not because Matthew actually wrote it. With those Gospels—the so-called apocryphal Gospels—that did not receive the Church’s seal of approval, their claims to be by apostles such as Thomas or Peter were rejected, because their doctrine was not recognized as apostolic."

- Introducing Eastern Orthodox Theology, p. 53