In Islam, Qira'at, which means literally the readings, terminologically means the method of recitation. Traditionally, there are 10 recognised schools of qira'at, and each one derives its name from a famous reader of Quran recitation. Each Qira'at is then transmitted via a riwaya (transmission) named after its primary narrator. Each of the riwayas is the whole of the Qur'an as recited by a master in all the variants which are transmitted from him. It is a corpus of recitation. The forms of each recitation are referred to by the notable students of the master who recited them. So we will find the turuq (transmission lines) of so-and-so, the student of the master. Then under the Turuq, there are also the wujuh. We find the wajh of so-and-so from the tariq of so-and-so. There are about twenty riwayat and eighty turuq.
According to hadith literature, the Quran is revealed in seven Ahruf (the plural of harf). The most famous of those hadiths is reported in the Muwatta compiled by Malik ibn Anas.
Malik Ibn Anas has reported:
Suyuti, a famous 15th century Islamic theologian concludes his discussion of this hadith:
And to me the best opinion in this regard is that of the people who say that this Hadith is from among matters of mutashabihat, the meaning of which cannot be understood.
Many reports contradict presence of variant readings:
The meaning of this hadith is explained as: (pp. 31)
As for the Prophet's words concerning the Quran, each of the ahruf has a border, it means that each of the seven aspects has a border which God has marked off and which no one may overstep. And as for his words Each of the ahruf has an outward aspect (zahr) and an inward aspect (batn), its outward aspect is the ostensive meaning of the recitation, and its inward aspect is its interpretation, which is concealed. And by his words each border ...... has a lookout he means that for each of the borders which God marked off in the Quran - of the lawful and unlawful, and its other legal injunctions - there is a measure of God's reward and punishment which surveys it in the Hereafter, and inspects it ...... at the Resurrection ......
Bilal Philips writes that the Quran continued to be read according to the seven ahruf until midway through Caliph 'Uthman's rule when some confusion arose in the outlying provinces concerning the Quran's recitation. Some Arab tribes had begun to boast about the superiority of their ahruf and a rivalry began to develop. At the same time, some new Muslims also began mixing the various forms of recitation out of ignorance. Caliph 'Uthman decided to make official copies of the Quran according to the writing conventions of the Quraysh and send them along with the Quranic reciters to the major centres of Islam. This decision was approved by Sahaabah and all unofficial copies of the Quran were destroyed. Uthman burned the unofficial copies of the Quran. Following the distribution of the official copies, all the other ahruf were dropped and the Quran began to be read in only one harf. Thus, the Quran which is available throughout the world today is written and recited only according to the harf of Quraysh.