The Epistle to the Hebrew is anonymous. Since it mentions “Timothy” as a companion, it is written “from Italy,” and it has essentially the same theology as Galatians, it is presumed to a prison epistle of Saint Paul – perhaps penned by Saint Luke on the Apostle’s behalf.

My own theory is that Luke-Acts-Hebrew is a Pauline dissertation packet prepared by Luke (see my book on this topic) for the Jews of Jerusalem and that the books were likely delivered together.

What’s interesting is how Hebrews came into the canon of the New Testament with regard to selection of book order:

Saint Jerome placed Hebrews after all the Pauline epistles and before the 7 Catholic epistles. This has become our received ordering of the epistles.

However, there are examples before Jerome of placing Hebrews within the Pauline corpus of epistles. For example:

1. One of our oldest manuscripts Papyrus 46 (dated between AD 175 and 225) places Hebrews between Romans and 1 Corinthians. It confirms that Christians in the second century believed Hebrews to by authored by Paul. This order is also found in minuscules 103, 455, 1961, 1964, 1977, 1994.
2. Codex Vaticanus (ca. AD 330) lists Hebrews between Galatians and Ephesians. This is either an error or left over from a previous manuscript from which Vaticanus was copied, because in the actual text of Vaticanus, Hebrews follows 2 Thessalonians.
3. This order (2 Thess > Hebrews) conforms to almost all of our earliest Greek manuscripts have Hebrews between 2 Thessalonians and 1 Timothy: Sinaiticus (ca. AD 400), Alexandrinus (ca AD 400), Ephraemi, H, I, P, 0150, 0151, and about 60 others.

It’s also noteworthy that in the Roman Rite liturgy of the Mass up until 1970, whenever Hebrews was read in the liturgy it was announced as “Paul to the Hebrews” with Paul stated explicitly.