There are several items I could clarify from my previous post. Maybe I’ll turn such clarifications into a series, though if you’ve read enough of this blog, you know that I’m very bad about finishing series. (I do plan to return to Zechariah, though I doubt I’ll get back to Calvin).
For now, I’ll just note that, as I previously wrote, Origen does not say that he derived the connection between the Hebrew alphabet and the Jewish canon from the Jews. Or, at least, he does not say so in the fragment of his commentary on the first psalm as preserved in Eusebius (HE 6.25). This is correctly perceived by Martin Hengel (Septuagint as Christian Scripture (2002), 62 n. 12).
However, in Fragment 3 of his Homilies on Lamentations, Origen does report that this tradition derives from the Jews. (See here for the 1901 GCS edition by Erich Klostermann, Origenes Werke 3, p. 236. And you better download it while you can. Next time you might not be able to find it.) Only the first paragraph is relevant. This is my translation.
Therefore the Hebrews say the books of the Old Testament are equal in number to the letters, so that they are an introduction to all divine knowledge, just as the letters are [an introduction] to all wisdom for those who learn. Therefore, they are quadrupled, perhaps because the elements of bodies are four.
The last sentence is a little confusing. My guess is that it refers to the four acrostic poems that make up the first four chapters of the Book of Lamentations (the last chapter, though containing 22 verses, is not an acrostic). Since these four acrostics each proceed through the entire Hebrew alphabet, Origen says that Lamentations has quadrupled the alphabet. He thinks the reason for quadrupling the alphabet (i.e. letters = “elements”) is to maintain an analogy with the four physical elements (earth, water, air, fire).
In any case, my point here is that this fragment definitely affirms that the connection between the 22 letters of the alphabet and the 22 books of the OT is current in the Judaism of Origen’s day. This should be considered when one tries to determine the chronological development of the Jewish canon. As Peter Katz showed long ago, and as, e.g., Gilles Dorival has emphasized of late (see references below), the 22-book canon has much better and earlier attestation than the 24-book canon. However, the 24-book canon appears already in 4 Ezra 14:45 and the Gospel of Thomas 52, so they must have co-existed in Judaism for several centuries. Much investigation has been done in this area, but more could be done.
Peter Katz, “The Old Testament Canon in Palestine and Alexandria,” ZNW 47 (1956): 191–217; repr. in S.Z. Leiman (ed.), The Canon and Masorah of the Hebrew Bible (New York: Ktav, 1974), 72–98.
Gilles Dorival, “L’apport des Pères de l’Église à la question de la clôture du canon de l’Ancien Testament,” in J.-M. Auwers and H.J. De Jonge (eds.), The Biblical Canons, Bibliotheca Ephemeridum Theologicarum Lovaniensium 163 (Louvain: University Press, 2003), 81–110.