Although it is a myth peddled by ignorant Westerners that Christians and Muslims believe in the same God, it is not a myth that we both claim to. The reason Muslims so often peddle the conspiracy theory that the Bible has been corrupted is that their Qur'an simultaneously claims the Bible is the authoritative revelation of Allah while constantly denying its doctrines.
If we assume, as the Qur'an does, that the Bible is "...what has been revealed to you from your Lord..." (Qur'an 5:68), and that "...None can alter His words, and He is the Hearing, the Knowing." (Qur'an 6:115), then we must accept that somewhere on Earth, there is a Bible that the Qur'an tells us "believe".
As it stands, there is no Bible anywhere on Earth that has ever confirmed Islam. If such a work existed, the Muslim argument would quickly switch from "The Bible has been corrupted" to "we have an uncorrupted, authentic Islamic Bible". But you will never see this shift in Islamic apologetics, because such a Bible does not exist. What does exist is a large number of Biblical manuscripts from before, during, and after the time of Muhammad. From these, many scholars have made painstaking effort to ensure that the Bible we have today is almost exactly as would have been read by its original audience.
This puts Muslims in an awkward position even as it is. If the Qur'an affirms the Bible, yet the Bible disconfirms the Qur'an, then there is no scenario in which the Qur'an can be true. The Qur'an, by confessing the truth of the Bible, has effectively screamed "don't believe me, believe the Bible instead". And this would be a satisfactory end of the argument. However, everyone loves a good sequel, and so it's worth noting that we can re-open the argument to not only show how the Qur'an disconfirms its own divine authorship by affirming the Bible, but also how it tells us where it really came from.
See, both books tell us a lot about "God", but the Bible also tells us a fair bit about Satan. It tells us about his personality, his desires, and his strategies to achieve the latter. In short, Satan is a liar and a murderer (John 8:44), full of pride, and desiring to be like God (Isaiah 14:12-21). He is constantly seeking souls to devour (1 Peter 5:8), and in that process, he takes men captive to do his will (2 Timothy 2:26). This often results in people killing Christians in the name of God (John 16:2).
When we read the Islamic sources, it describes Satan in a similar way. He is this great enemy of man and God alike, deceiving man and seeking to subvert the will of Allah. They also add a number of really strange things, such as giving instructions on how to wash Satan out of your nose when you wake up (Sahih Bukhari Volume 4, Book 54, Hadith Number 516), but in Islam, Satan is nevertheless ascribed the same adversarial status as in Christianity.
However, while the Qur'an gives lip service to Satan being the ultimate bad guy, note how it describes Allah. In the Qur'an, he is obviously supposed to be "God", but his personality reflects a very different being. As a father to no one, Allah is quite antagonistic towards mankind, and in particular, to Jews and Christians. It is ironic that in the beginning, Islam spoke very highly not only of our Scriptures, but also of us. However, as time went on, and we of course rejected Muhammad's "revelations", the revelations became increasingly hostile towards us. Eventually, we became "the worst of creatures" (Qur'an 98:6), whom Muslims are not to take as friends, for we are friends of each other, and that to take us as friends is to become one of us (Qur'an 5:51).
But then, what else can we expect from the greatest of deceivers? Who do I mean here? I could mean Satan, who, as we have already established, "...was a murderer from the beginning, and does not stand in the truth, because there is no truth in him. When he speaks a lie, he speaks from his own resources, for he is a liar and the father of it." (John 8:44). But actually, the Qur'an repeatedly affirms that the greatest of deceivers is Allah!
Establishing this is actually quite tricky. Not because it isn't true, and I have to pull some kind of sneaky trick to do so, but because it requires at least one of four things:
1. An accurate translation of the Qur'an in the English language.
2. A deep knowledge of Arabic.
3. A semi-accurate translation of the Qur'an with detailed footnotes.
4. The ability to determine, based on context, the sense of a given word.
Several verses throughout the Qur'an describe Allah as the best of deceivers. Qur'an 3:54, 7:99, 8:30, and 10:21, all do this. However, in English, it is typically rendered the best of "plotters", "schemers", or "planners". However, the word here is "makura", from the root word "makr", which specifically means deception. Thus, not all English translations of the Qur'an render the word in such diplomatic terms. The Muhammad Ahmed-Samira translation, for example, renders 3:54 "And they cheated/deceived and God cheated/deceived, and God (is) the best (of) the cheaters/deceivers."
If you know the Arabic, you don't necessarily need an English translation to see that the minority rendering is quite accurate. But if you don't know Arabic, you have reason to doubt. Perhaps this is just some play by Christians to make Islam look even more grotesque. That's where footnotes come in. Any good translation of any work, religious or otherwise, will contain footnotes to highlight or explain certain disputes. Bibles do this quite often, especially study Bibles. The Qur'an is no different. Many translations do contain footnotes, such as the example shown below (original image shared by David Wood).
As you can see, even in translations where "planners" is the chosen rendering, it must be admitted that the root of the word is "deceive", thus legitimising Allah's status as the best of deceivers.
But perhaps this still isn't enough. There are English translations of the Qur'an that admit Allah is the best of deceivers. This is so true to the Arabic that even Muslims who choose alternative renderings acknowledge it. But we are talking about a root word here, so is it possible we're just committing the root fallacy? Let's take our eyes off the word for a moment and ask about the context in which it is being used.
Of course, not every instance of Allah being the best of deceivers addresses the identical example. However, sticking with 3:54, the context is the central event of the Christian faith: The death and subsequent resurrection of Jesus. After the announcement of His birth to Mary (v3:45-47), Jesus confirms the Torah and the Gospel (v48-50) and Monotheism (v51), Jesus senses disbelief (v52), and asks who follows Him. His followers affirm their loyalty (v52-53). This is where the disbelievers begin to scheme, but Allah schemes too, and is the best of schemers (v54).
For now, this is all fine and dandy. We could make the connection between the obviously dishonest schemes of the people against Jesus and say that, since it's the same word, Allah presumably schemes in the same way, but this seems to be a little too snakey. So, we move on to verse 55, which says, in the Sahih International translation, "[Mention] when Allāh said, "O Jesus, indeed I will take you and raise you to Myself and purify [i.e., free] you from those who disbelieve and make those who follow you [in submission to Allāh alone] superior to those who disbelieve until the Day of Resurrection. Then to Me is your return, and I will judge between you concerning that in which you used to differ."
On its own, verse 55 doesn't tell us much. It does leave us with another problem, leading directly back to the original Islamic dilemma, but we'll address that again in a moment. For now, note that a little while on, in Qur'an 4:157-48, we read "And [for] their saying, "Indeed, we have killed the Messiah, Jesus the son of Mary, the messenger of Allāh." And they did not kill him, nor did they crucify him; but [another] was made to resemble him to them. And indeed, those who differ over it are in doubt about it. They have no knowledge of it except the following of assumption. And they did not kill him, for certain. Rather, Allāh raised him to Himself. And ever is Allāh Exalted in Might and Wise."
The fullness of Allah's scheme, therefore, is revealed, and it is quite deceitful. Unbelievers really don't like Jesus, so they conspire to kill Him, and they think they've succeeded. But Allah, clever little devil that he is, was a few steps ahead of them. Before the event, in verse 55, Allah promises to raise Jesus to himself. Then, in the next Surah, we see that Allah does exactly that... but Jesus' enemies thought they killed Jesus because they killed some other poor victim who was made to resemble Jesus.
But the deception goes deeper! See, previously, Allah had promised Jesus "...indeed I will (...) make those who follow you [in submission to Allāh alone] superior to those who disbelieve until the Day of Resurrection." (Qur'an 3:55). But the day of resurrection has not come. It had not come between the time of Jesus' ascension and Muhammad's reign of terror, nor has it come since Muhammad's reign of terror until today. Yet, those who followed Jesus directly testified to His death and resurrection. In other words, Allah is so unbelievably deceitful that he not only makes it look like someone else is Jesus so he gets killed instead, but in so doing, he deceives the followers of Jesus into thinking Jesus is dead. Then Jesus comes back to them, and affirms, in Allah's own revealed books, that He has died and risen again for sin!
Now, I suppose one could call this a "plot", or a "scheme", or a "plan". But let's be honest here: It is the most deceitful scheme of all. It is such a deceitful scheme that it started a religion so much more prominent in the world than Islam has ever been, or will ever be.
Of course, this deceit never took place. God cannot lie (Titus 1:2), and His Holy word affirms the death and resurrection of the Lord Jesus' Christ. But according to the unholy Qur'an, Allah did deceive the entire pre-Islamic world into believing Jesus died. To the Jews, His death was permanent, and any evidence of His resurrection was illusory. To the Romans, His death was justly deserved, and all claims that He had risen victorious were treasonous against Caesar. To the Christians, His death was temporary, and by it, He had paid for our sins, before raising to life as the firstborn from the dead.
So who is Allah most like? I he truly like God, who revealed the Torah and the Gospel? Or is he, being the greatest of deceivers, more like Satan, whose desire to be like God was so great, it resulted in him being removed from his Heavenly post? Undoubtedly, Allah is the devil; a deceitful being whose sole purpose in this life is to steal the souls of men. His fate is an eternity in Hellfire, where Muhammad, if he truly existed, will likewise dwell.
But we, whose lungs still hold breath, do not have to share this tragic fate. See, contrary to the cold personality of Allah, God's heart is full of love for all mankind. Furthermore, "...God demonstrates His own love toward us, in that while we were still sinners, Christ died for us." (Romans 5:8). If you're a Muslim reading this, God loves you. Your sins, which at this point include blasphemy, can be forgiven. But only through the blood of Jesus. You must repent, and confess Him as the risen Lord. Only then will you know true salvation, which Allah could never, and would never offer you.