The Biblical Canon of
Hilary of Poitiers

The Canon of Hilary of Poitiers (ca. 310-ca. 367) is included in the introduction to his commentary on the Psalter (the Tractatus super Psalmos), which he wrote around 365 A.D.  Hilary’s Tractatus super Psalmos begins with an introduction called the Instructio, in twenty-four chapters.  It is in Chapter 15 of the Instructio Psalmorum that Hilary gives a list of Old Testament books.  His reasoning behind the number of books listed is due to the tradition that the number corresponds with the alphabet;

“And this is the cause that the law of the Old Testament is divided into twenty-two books, that they might agree with the number of letters. These books are arranged according to the tradition of the ancients, so that five are of Moses… complete the number of twenty-two books. To some it has seemed good to add Tobias and Judith, and thus constitute twenty-four books according to the Greek alphabet.” -Prologue to the Book of Psalms 15, by Hilary of Poitiers

He essentially lists the books of the Jewish canon, except that he includes the Epistle of Jeremiah as a part of Jeremiah, as well as Lamentations.  He titles the book of Esdras as ‘Words of the Days of Esdras’, which isn’t clear whether he intended to include one or both books of Esdras. After naming each of the twenty-two books, he also acknowledges that some people include Tobit and Judith so as to correspond with the Greek alphabet.  He does not ever address a New Testament canon.  Despite the list given here, Hilary apparently saw no issue with quoting other Deuterocanonical books, such as Maccabees, as Scripture;

“Since, therefore, the words of the apostle, one God the Father, from whom are all things, and one Jesus Christ, our Lord, through whom are all things, form an accurate and complete confession concerning God, let us see what Moses has to say of the beginning of the world. His words are, ‘And God said, let there be a firmament.’ If you deny it, you must tell us through whom it was that God’s work in Creation was done, or else point for your explanation to an obedience in things yet uncreated, which, when God said, ‘Let there be a firmament,’ impelled the firmament to establish itself. Such suggestions are inconsistent with the clear sense of Scripture. ‘For all things,’ as the prophet says, ‘were made out of nothing’ [2 Maccabees 7:28]; it was no transformation of existing things, but the creation into a perfect form of the non-existent.” -Hilary of Poitiers, On the Trinity, Book 4, 16.

Sources: 

• Edmon L. Gallagher and John D. Meade. The Biblical Canon Lists from Early Christianity:  Texts and Analysis.  Oxford University Press. 2017