However, those who maintain the belief in alteration may claim that the obliga‌ tory recital of a complete sura [i.e., as it was revealed] has been abrogated by the obligation to read any complete sura as it is in the existing Quran. At any rate, we do not believe that they would maintain such a thing, because abrogation has definitely not occurred after the [lifetime of the] Prophet, although there has been a discussion among scholars about its possibility, or otherwise-a subject that is beyond our scope at this time.
To summarize, there is no doubt that the Imams ordered their followers to recite
any sura from the Quran that is in our hands for the performance of the daily prayer. This injunction is well established, without any shade of doubt, nor any possibility that it was made as a precautionary dissimulation, and it must have been ordained either during the time of the Prophet or after that [under the Imams]. The latter propo‌ sition, however, is wrong because it would have amounted to an abrogation [of a practice of the Prophet], and this certainly did not take place after [the time of] the Prophet, though in itself it is possible. Thus, it is necessary to regard [the religious ordinance pertaining to the recitation of a complete sura in the prayer] as the estab‌ lished practice from the time of the Prophet himself. In other words, this means that no alteration has been made in the Quran. This form of argumentation applies to every legal ordinance that the Imams have made incumbent in the recitation of a complete verse from the Quran.

Assertion about Alteration under the Caliphs

The fifth argument [that alteration did not occur involves the following]. Those who maintain the belief in alteration claim that it took place either under the first two caliphs (Abu Bakr and Umar), after the death of the Prophet (peace be upon him and his progeny), or under Uthman when he assumed the affairs of the community, or under some other person when the first period of the caliphate ended. All these assertions [about when it occurred] are incorrect. As for the charge that the alteration took place under Abu Bakr and Umar, it is negated by the following. If they did alter the Quran, this was either done unintentionally-because of the fact that the complete text of the Quran was not available for them, having not been compiled by then-or it was done deliberately. If they had deliberately altered the Quran, this would have in‌ volved either the verses that adversely affected their leadership or verses that did not have such an effect. The possibilities are therefore three in number.
As for the possibility that the complete text of the Quran had not reached them,
this is unquestionably wrong. The attention which the Prophet paid to the Quran‌ memorizing it, reading it, and reciting its verses-and the attention which the Com‌ panions, likewise, lavished on the Quran, both during the Prophets lifetime and af‌ ter his death, lead us to the definitive conclusion that the Quran was preserved with them, whether in the form of a collected text or fragments; memorized in their hearts; or written on paper. If they had paid so much attention to memorizing pre-Islamic Arabic poetry and orations, it is hard to imagine that they did not pay similar attention to the preservation of the Book of the Almighty, [especially when] they had risked death by calling for and announcing its ordinances, and, for its sake, had emigrated