This is why even those who postulated the borrowing theory like Phillip Hitti were forced to concede that '...the resemblances do not warrant the conclusion of borrowing or quoting or that he was not a slavish imitator.' [Philip K. Hitti, Islam and the West: A Historical Cultural Survey, 1979 (Reprinted), Robert E. Krieger Publishing Company, New York, pp. 17-18.]
Richard Bell, who was at pains to prove the direct dependence of Prophet Muhammad صلى الله عليه وسلم on the Bible also insists that he was not working on any real acquaintance with the Bible itself. [Richard Bell, The Origin of Islam in its Christian Environment: The Gunning Lectures Edinburgh University, 1925, London: Frank Cass and Company Limited, 1968 (Reprinted), p. 112.]
Well, the thesis that Islam is a “continuation” is purely theological and fits Muhammad’s teleological proposal, but it is not necessarily the truth. In fact, this “justification” is very extremely
convenient, as it perfectly explains why there are similarities and also differences with other sacred books. I find it very suspicious when someone says, “Everything that is similar is true, everything that is different was corrupted, but I received the true message, so everything I say is the final truth and you must believe it.”
I find this even more suspicious when the books Muhammad draws parallels to (like the Torah and the Gospel) contain ideas that are so distinct—as you yourself pointed out in the Torah—and they came millenniums before him, and for many of these, there is no historical basis at all to suggest corruption, whether minor or major. So logically, for what Muhammad says to be true, Moses himself would have had to invent things or record them incorrectly, and then Muhammad, millenniums later, would have “corrected” them. I’m sorry, but from a historical and logical perspective, this is highly questionable and simply unreliable, in my opinion. Of course, everyone has their own worldview.
Regarding how the Prophet could have known everything he knows, it is not impossible that he, or someone around him, had some contact (even minimal) with external religious traditions. Religions have borrowed concepts and figures from other religions throughout entire human history, and this does not imply deep or comprehensive knowledge of the other religion. One example: if someone reads our conversation here, they will get a very good sense of both faiths—their disagreements and agreements, arguments, and various theological concepts of each. Even without prior knowledge. Now, do you really think it’s 100% impossible that Muhammad had some contact,
even minimal, with other cultures? That would simply be incorrect, especially considering what I mentioned about this same topic in messages above.
Another point I want to raise, again with all due respect and reverence for your faith, is that it is also possible Muhammad could have encountered a deceptive angel, one that was not truly an angel, especially considering the very peculiar nature of the angelic encounter he reported. Remember that Jesus himself says in Matthew 24:24:
“For false Christs and false prophets will appear and perform great signs and wonders to deceive, if possible, even the elect.”
Notice the term “false Christs”—this does not necessarily refer to a person impersonating Jesus (that would make even sense), but to a message that contradicts what He actually said and could deceive even the faithful. 1 John 4:1–3 also warns us:
“Beloved, do not believe every spirit, but test the spirits to see whether they are from God; for many false prophets have gone out into the world. By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God; and every spirit that does not confess Jesus is not from God.”
So even if there were miracles (which I haven’t seen much), this was already predicted in the Bible, which warns us not to trust everything blindly.
It is also worth noting that the Qur’an does not only draw parallels with the canonical Old and New Testaments. As I mentioned before, it also makes very clear parallels with ideas that exist only in apocryphal gospels and nowhere else. These gospels, as I said, were often not written with theological aims, but rather as attempts to explain certain concepts of faith. You mention a “lack of historical credibility” of the Gospels (which is a fallacy), but some of these apocryphal gospels—among other books that Muhammad parallels—appeared centuries after Christ and the apostles and were never attributed to the apostles by the early Church, unlike the canonical Gospels.
I can provide explicit examples of clear parallels and explain why the respective books are not reliable, if you want.