Hafiz (Quran)

Hafiz (Arabic: حافظ‎‎, ḥāfiẓ, Arabic: حُفَّاظ‎‎, pl. huffāẓ, Arabic: حافظة‎‎ f. ḥāfiẓa), literally meaning "guardian" or "memorizer," depending on the context, is a term used by Muslims for someone who has completely memorized the Qur'an. Hafiza is the female equivalent.

The Islamic prophet Muhammad lived in the 6th Century CE, in Arabia in a time when few people were literate. The Arabs preserved their histories, genealogies, and poetry by memory alone. According to countless books of history, when Muhammad proclaimed the verses later collected as the Qur'an, his followers naturally preserved the words by memorizing them. Approximately eight months after the death of the Prophet, the entire Quran was written down by his companions (sahaba), anywhere from 10,000 to 150,000 had it memorized perfectly at the time of its inscription, ensuring the authenticity of al-Qur'an.

The Arabic writing of the time was a non-marked script, that did not include vowel markings or other diacritics needed to distinguish between words. Hence if there was any question as to the pronunciation of a verse, the memorized verses were a better source than the written ones. The huffaz were also highly appreciated as reciters, whose intoned words were accessible even to the illiterate. Memorization required no expensive materials; at the time there was no paper in the Muslim world, only vellum.

...
Wikipedia