Arthur Jeffery is often the source of textual criticism of the Qur'an which alleges that the Qur'an is not preserved and complete in its present version - an earlier post about comparative textual criticism can be found here). Alhamdulilah Muhammad Mustafa al-Azami has written a comprehensive and scholarly text that refutes those claims. I've quoted some sections here for our collective benefit inshaAllah:
"Arthur Jeffery examined 170 volumes to compile a list of variant readings which take up roughly 300 pages in printed form, covering the so-called personal Mushafs of nearly thirty scholars. Of this total he reserves 88 pages for the variations allegedly coming from Ibn Mas'ud's Mushaf alone, with another 65 pages for Ubayy's Mushaf, dividing the reminder (140 pages) between the other twenty-eight. The disproportionately high variance rate attributed to Ibn Mas'ud makes his Mushaf worthy of closer inspection; some of the claims raised by Jeffery against it are: That it differs from the Uthmani Mushaf in its sura arrangement, in its text, and that is omits three suras.
"He levies all these charges even though no one, including his sources, has ever witnessed a 'Mushaf' with all these alleged variances. In truth none of his references even mentions a 'Mushaf' of Ibn Mas'ud; instead they use the word qara'a, in the context of "Ibn Mas'ud recited such-and-such verse in this way". A cursory glance at his sources yields two objections straightaway. First, because they never state that Ibn Mas'ud was reading from a written copy we can just as easily assume that he was overheard reciting from memory, and how can we confidently deduce that the erroneous readings were not due to a memory slip? Second, the vast majority of Jeffery's references contain no isnad whatsoever, making them inadmissible because they offer nothing but empty gossip. (p. 195)
"I mentioned above the need for some kind of certitude about Ibn Mas'ud's Mushaf. While researching variant readings, Abu Hayyan an-Nahawi noticed that most of the reports were channeled through Shiite sources; Sunni scholars on the other hand stated that Ibn Mas'ud's readings were in line with the rest of the umma. (p. 197)
"Embarking on any research requires a solid footing, whereas here we discover ourselves drowning in a sea of hearsay that carries almost no transmission chains and that fails to provide any coherent view of what 'Ibn Mas'ud's Mushaf' might have been. Under the circumstances Jeffery's approach and findings, we can see, are fundamentally flawed. (p. 198)
"Hammad ibn Salama reported that Ubayy's Mushaf contained two extra suras, called al-Hafad and al-Khala. This report is completely spurious because of a major defect in the chain, as there is an unaccounted for gap of at least two to three generations between Ubayy's death and Hammad's scholarly activity. Besides this, we must remember that a note written in a book does not make it a part of the book. (p. 203)
"Judeo-Christian scholars have long cast their eyes toward the Qur'an in search of variances, but so securely has Allah preserved His Book that their vast efforts and resources have yielded them little more than fatigue ... Jeffery acknowledges this fact bleakly, lamenting that, "Practically all the early Codices and fragments that have so far been carefully examined, show the same type of text, such variants as occur being almost always explainable as scribal errors ... Stripping away all Qur'anic terminology Wansbrough speaks instead of Haggadic exegesis, Halakhic exegesis, and Deutungsbedurftigkeit. Everyone also refers to canonisation of the Qur'an, and the codices of Ibn Mas'ud. The vast majority of Muslims live in total ignorance of this jargon. While the hypothesis of Jeffery, Goldziher and others have been dealt with and dismissed, we have yet to fully gauge the motives behind such efforts. (p. 208)