If Muhammad’s detractors are correct, in what language would such an informant (or, for that matter, any of the Qur’an’s first auditors) have known the Bible? Griffith does not dispute that Jews and Christians spoke Arabic before the emergence of Islam, nor that they may have conducted liturgies in Arabic. But he does refuse to posit a written Arabic Bible before the rise of Islam. The background of this claim is his decades-long engagement with Irfan Shahid, who argues that the Gospels and Psalms existed in Arabic before the rise of Islam. Locating extant parchments from late antiquity and the early medieval period that could constitute evidence in this debate is difficult, given the usually poor condition of any manuscript of such an early provenance. Nonetheless, Griffith demonstrates how the evidence we do have “argues against [the] probability” of a pre-Islamic Arabic translation of the Bible.And then there's this:
Scholars interested in heterodoxy will be excited to learn of Arabic translations of apocryphal and pseudo-epigraphical texts that, previously, had been thought to exist only in Greek or Syriac fragments or in a single Syriac source (such as Sinai Arabic MS 389, which contains three Arabic translations of the Apocalypse of Baruch, the Epistle of Baruch, and 4 Ezra).This sentence could be phrased a little more clearly, but it could be taken to refer to the recovery of new Arabic translations of biblical apocrypha and pseudepigrapha. Yes, this sounds exciting. But not so much if the reviewer just means the Sinai manuscript, which is already well known.