1/2 Hey !

So I am really not an expert on this, but I am going to try to give some kind of answer, despite the thread being one month old (!).

First, a small remark. Your initial comparison regarding the Quran and the Bible seems to imply some kind of adequacy in terms of corpus (as Quran and Bible are the sacred text for the Muslims and the Christians, and are at the core of their faith). But I am not sure it should be compared as such, as a very important part of the fundamental Islamic religious corpus progressively came to include the Prophetic hadiths, that is everything the Prophet Muhammad was considered to have said and done, reported generation after generation through oral transmission, which emerged as a (mostly) fixed corpus by the 9th and 10th century. This is a HUGE corpus, as the number of hadith (and here I am talking about so-called “authentic hadith” (sâhîh)) reported is said to comprise between 900 and more than 100 000 traditions. This corpus was also, for many scholars, partially memorized. So the comparison in terms of words may not be judicious, as it’s likely that the total number of words many scholars (although far from all) from the Islamic worlds were memorizing from the fundamental religious corpus was, for well-educated Medieval Islamic scholars, and especially muhaddithûn (specialist of Prophetic traditions), at least comparable to the entire Bible, if not much more important. All the more since from the 10th centuries onward the study of Prophetic traditions became widespread, including for people not specializing as muhaddithûn.

So, it seems to me your questions more broadly touches upon with the issue of memorization and scholarly knowledge in the Islamic worlds and the Christian worlds, and as far as we know indeed memorization and oral transmission was a common practice in the scholarly environment of the Islamic worlds.

The question of memorization may be partially linked, as you suggest, to the Quran itself, but also to the progressive development of the scholarly environment in the Islamic domains. There are few reasons that may be advanced as to the development of memorization.

In 7th century Arabia, and more generally everywhere during the so-called Medieval period, people were likely than not illiterate, and so could not read. This did not mean that they could not know the Quran or other texts. In fact, poetry, probably one of the main vehicles of communication in Arabia before Islam and in the early Islamic Middle East, was quite spread out. So in fact much of the texts were read out loud.

This leads to the nature of the Quran, as it is itself a versified rhymed prose text. All verses of the Quran rhyme with following or preceding verses with pausal rhymes as the norm, which presents some contrasts with many pre-Islamic poetic texts, but it has been considered by some as poetry and the form of the text in any case encouraged both orality and recitation, as poetry was designed for oral recitation during public performances.

In fact, one of the possible meanings of the word qur’ân linked to the act of recitation, as much as to reading, from the root qa/ra/‛a. Thus, the Quran was first and foremost, initially, a recitation (by the Prophet, and then by people that had memorized it or parts of it). Bits of it were also said to have been written on a vast array of different material by the time of Muhammad (d. 632), including wood, rocks, parchments. By 644, there were only a few numbers of “complete copies”, and one version finally came to emerge between 644 and 654, or so the Islamic Tradition tells us. This is the so-called ‛Uthmân vulgate (from the Commander of the faithful, ‛Uthmân, then ruler of the then fast-expanding Islamic domains). That is basically the primitive version of the Quran we know of today, although diacritic elements (for pronunciation) were added later.

This means that the Quranic text was widely recited. This may have strengthened the need to memorize it, especially considering the price of parchments and papyri, before the wide-spread diffusion of paper in the Islamic domains from the 8th century onward (Bloom, 2001, chapter 2). Even then, manuscripts were not cheap.

That being said, on the one hand the process of memorization of the Quranic text, but more generally the process of memorization, is also encouraged within the Quran itself (Quran, al-Ahzab 33:34; Quran, al-Qamar 54:17), an encouragement maybe also prompted by the importance to recite the Quran as stated in the Quran itself (Quran, al-Muzzammil 73:20, “So recite 'in prayer' whatever you can from the Quran”). Prophetic traditions also tend to insist on the merits of memorizing the Quran (“He who reads the Quran and memorizes it is to be assembled [on the Day of Judgment]” – al-Bukhârî)

This importance to recite the text is also to be understood in relation to the nature of the Quran, which is the supposed word of God Himself. So any kind of recitation was basically part of an expression of faith and a direct address to God, hence also the importance to know the Quran.