I have previously asked a question that a Christian asked to me but he is bothering me again,I think he is trying to convince me to leave Islam.But before I block him I think I need to find the answer that he raised,he quoted this"The accounts of non-Muslim conquered peoples also conflict with the accounts of traditional Islamic literature. Examining 7th century Byzantine Christian sources commentary on the Arab "immigrants" (Mhaggraye) who were invading and settling in formerly Byzantine territory at that time, historian Abdul-Massih Saadi found the Christians never mentioned the terms "Quran" nor "Islam" nor that the immigrants were of a new religion.[Note 2] They referred to the immigrants in ethnic terms -- "among them (Arabs) there are many Christians...". The Christians used secular or political, not religious terms (kings, princes, rulers) to refer to the Arab leaders. Muhammad was "the first king of the Mhaggraye", also guide, teacher, leader or great ruler. They did however mention the religion of the Arabs. The immigrants' religion was described as monotheist "in accordance with the Old Law (Old Testament)". When the Emir of the immigrants and Patriarch of the local Christians did have a religious colloquium there was much discussion of the scriptures but no mention of the Quran, "a possible indication that the Quran was not yet in circulation." The Christians reported the Emir was accompanied by "learned Jews", that the immigrants "accepted the Torah just as the Jews and Samaritans", though none of the sources described the immigrants as Jews."Can anyone tell me about the quotation?Is there any possible misunderstanding here?
I have found the source cited:
It is cited in Wikipedia
History is not changed by belief. Still, the perspective of any historical document as well as a recent text of dissertation has a certain focus, based information, perception, standards and belief.
The paper of Abdul-Massih Saadi focuses on early Syriac documents that are neither influencedby Islamic sources nor by Byzantine opinions.
Of course, the view in the paper - as any paper in Historical science - is not and does not claim to be an ultimate truth. Still, I think this is an interesting paper, and it allows to study in debth reading the cited sources that were close to the events but still seen from outside Islam.
We should never fear the truth. Even less, we should fear and discard historical documents. They are not the truth but just views on the whole from the perspective of a writer.
The paper cites (it does not say it is true!):
John of Phenek describes the Mhaggraye’s beliefs as worshippers of One God in accordance with the old Law (Old Testament)
It is an external view from a Christian writer. In his view, Islam seemed close to Judaism because it confirms many Jewish laws that had been abandoned by the Christians. In contrast, a Jewish view would probably see Islam as a Christian religion because it confirms Jesus as the Messiah.
Everyone sees something different according to his perspective, be it the writer or the reader of the documents. Your Christian interlocator seems to see something against Islam in it; I don't see the cited paper the same way. We need not defend our religion beyond truth and evidence. And truth and evidence is at its best indicated, but hardly given by historical documents. So keep calm and study the documents with a critical distance and without fear.
Is it possible that in 640 CE the Quran was not yet in circulation?
Muhammad (p.b.u.h) died in 632 CE. The document cited is dated 644 CE, 12 years after Muhammad's death. This is before the Quran had found its final form under Uthman ibn Affan who reigned from 644–656. At that time, the Quran was not a book; it had been written down in several notes, but the main usage and tradition was that it was recited.
The word Quran was used before the Holy Quran we are talking about was revealed. Is was a term for liturgical Christian writings, comparable to a lectionary or a hymn book, containing contents that was read, recited or chanted, and most Christians never held it in their hands but learned it in the service. The usage of the Holy Quran was somehow similar to this although the awareness for the importance of its contents was for sure other, not comparable to the importance Christians gave to the preceding Christian homologues.
It is thus well possible that the Quran was not counted among the scriptures at that time. We find the same in early Christian documents like the epistles of Paul, written 10-20 years after Jesus (p.b.u.h), who, if he talks about the Scripture or the Law, he does not mean the Gospel but the Tanakh. He still uses the term Euangelion in its original sense: The Good Message; the Message of God through Jesus (p.b.u.h).
In fact, reading the Quran, I also have the impression that the "Book" (the Tanakh and the Gospel) has been confirmed and completed with the last revelation, not invalidated and replaced. In this sense, I would not be suprised if the first Muslim generation still held to this attitude. Nevertheless, at least in what I read in the paper, it is not fully clear whether the passage that lead to the conclusion
(the) author refers to Mhaggraye as having accepted the Torah—not the Gospels—just as the Jews and Samaritans
really refers to Muslims. It is also possible that those people were in fact Jews from Arabia; the rejection of the Gospel would rather imply this.
Note that the understanding of «Mhaggraye» is drawn from several scriptures.
The descendant of Abraham through Ishmael and Hagar worshipping at the kaaba
may apply to the old arabic religion as well as for the new one.
The description of John of Phenek:
Directly, John of Phenek describes the Mhaggraye’s beliefs as worshippers of One God in accordance with the old Law (Old Testament). John continues that the Mhaggraye held the instructions of Muhammad, who became their instructor (Taraa/ mhadyana); and they were inflicting the death penalty on any persons violating Muhammad’s instructions.
definitely refers to Muslims. It refers to the view of a contemporary Christian; see the first (original) part of my answer.
Citations from the cited source:
 Abdul-Massih Saadi, “The Letter of John of Sedreh: A New Perspective on Nascent Islam,” Karmo 1.1 (1998)  A. Mingana, Sources Syriaques, p. 146 (Syriac) / p.175(French).  Abdul-Massih Saadi refers to the same source and page as , but I did not find the passage in there.