One important takeaway from the book of Job is just how much control God has over Satan. Satan, contrary to the popular caricature, is not God's equal. He is not even a worthy opponent, for no such characters can be found. Satan is barely an annoying itch on God's shoulder. As much as Satan can do to us, He can't even get God's attention if God isn't willing to give it.
But if God is willing, Satan can get God's attention, and he can request permission to do evil. Sometimes, in His wisdom, God allows this. Yet with limits. Satan was permitted to torment Job, yet was at first not permitted to touch Job himself. Job passed this test, maintaining his faith. So Satan again asked permission to torment him, and was this time allowed to attack Job's health, yet with the provision that his life be spared. With all this, we see that while God will allow Satan to do evil, Satan can't do a thing without that consent. Even as eternity's greatest sinner, Satan can't do a thing if God doesn't let him.
I firmly believe that the Qur'an is a work of Satan. Allah even closely mirrors all of Satan's attributes, right down to Allah being called the best of deceivers (Qur'an 3:54; 8:30). Satan, of course, is the father of lies (John 8:44), whereas God is not a man that He should lie (Numbers 23:19), and indeed cannot lie (Titus 1:2). So if indeed there is anything supernatural behind the Qur'an, it is not from God, but from Satan.
But just as the Lord told Satan "Behold, all that he has is in your power; only do not lay a hand on his person", it would appear that He also told him something like "behold, Muhammad's religion is in your power, only you must cause him to affirm my scriptures." Why do I say that? Because Muhammad did, indeed, affirm the scriptures of the Jews and the Christians, as is evident from both the Haddith, and more importantly, the Qur'an. Let's look at some Qur'anic examples. All quotations are taken from the Sahih International translation available for free on quran.com
"[Mention] when Allah said, "O Jesus, indeed I will take you and raise you to Myself and purify you from those who disbelieve and make those who follow you [in submission to Allah 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." (Qur'an 3:55)
This verse does not directly refer to the Christian scriptures (don't worry, that's coming), but note that Allah is very clear on this. He will "make those who follow you superior to those who disbelieve until the Day of Resurrection". Now, needless to say, the Day of Resurrection has not happened yet. Therefore, if Allah is a man of his word (of course, we know he isn't, but if Muslims want us to believe the Qur'an at all, we must assume 3:55 is a hard promise), the followers of Jesus are still superior to the disbelievers. Now, for all of history, from the day Christ ascended to Heaven right to the day Muhammad first claimed to be a prophet, all the way until this very day, what have Christians been preaching? We've been preaching that Jesus is the divine (Muslims deny His divinity) Son (Muslims deny Jesus is the Son of God) of God, who died on the cross (Islamic theology claims Jesus never got crucified, but Allah, the "best of deceivers", deceived people into thinking He did) by the will of the Father (Muslims deny Allah is the Father of anyone). If the followers of Christ are superior until the Day of Resurrection, and the followers of Christ that are dominant are the Christians, we can only assume, based on Qur'an 3:55, that Allah's blessing is not upon Islam, but upon Christianity.
Qur'an 61:14 agrees, as it says "O you who have believed, be supporters of Allah, as when Jesus, the son of Mary, said to the disciples, "Who are my supporters for Allah ?" The disciples said, "We are supporters of Allah ." And a faction of the Children of Israel believed and a faction disbelieved. So We supported those who believed against their enemy, and they became dominant."
Now, if any person believed Muhammad's version of Jesus before Muhammad, they were anything but dominant. As a matter of fact, they were so not dominant, we have no record of their existence. And believe me, we have records of heretics. We have people who believed Jesus was 100% man, 0% God. We have records of people who think He remained dead, rising only as a spirit. Within the scriptures, we have evidence of Gnostics, who believed Jesus was a phantom, merely appearing as flesh and blood. We even have fraudulent gospels from the second century that, frankly, are crazy enough to be not worth studying. But we have no record of any Christian, orthodox or heretical, preaching anything that could be considered Islam. The dominant Christians from both before and after the time of Muhammad preached a Jesus that is anything but Islamic.
In Qur'an 5:47, we read "And let the People of the Gospel judge by what Allah has revealed therein. And whoever does not judge by what Allah has revealed - then it is those who are the defiantly disobedient."
It can be disputed exactly what is meant by the Gospel here, however it is beyond dispute that Muhammad meant at least one book in the possession of the Christians. In his theological ignorance, it is not beyond imagination that Muhammad may have referred to the entire New Testament as the Gospel. However, for the sake of generosity, we will allow for him to have been referring to what Christians were then calling "the Gospel". From the second century until Muhammad's time (and even by some Christian circles to this very day), that would be the fourfold Gospel that is Matthew, Mark, Luke and John. We can even afford to let Muhammad even further off the hook and just limit it to one of the Gospels.
However much of the New Testament we allow Muslims to shave off, Muhammad in the Qur'an tells us that whoever does not judge by what Allah has revealed in there is "defiantly disobedient".
Muhammad actually digs a further hole in Qur'an 5:68, when he says "Say, "O People of the Scripture, you are [standing] on nothing until you uphold [the law of] the Torah, the Gospel, and what has been revealed to you from your Lord." And that which has been revealed to you from your Lord will surely increase many of them in transgression and disbelief. So do not grieve over the disbelieving people."
When Muhammad says "the Torah", there can be no dispute that he referred to this book correctly; the same Torah we have today. Why? Because in Sunan Abu Dawud, Book 38, Number 4434, Muhammad is asked to judge a dispute. He asks for a Torah, and he is given one. He then places it on the judgement seat and proudly announces "I believe in you and the One who revealed you". So, indisputably, Muhammad wanted Jews to judge by the Torah, even claiming that the Jews had no ground to stand upon unless they judged by the Torah.
But it gets worse, because once again he refers to not only the Gospel, but "what has been revealed to you from your Lord". Now, say that to a Christian, what are they going to think of? They're going to think of the Bible. No dispute, no questions asked, if you say to a Christian "judge by the Torah, the Gospel and that which has been revealed to you by your Lord", we are always going to think of the Bible. By Muhammad's day, there wasn't even room for dispute regarding the New Testament canon.
Now, I could go on, and initially, I had planned to. There are many places in which the Qur'an explicitly affirms the inspiration, preservation and authority of the Judeo Christian Bible. So, while I believe Satan inspired the Qur'an, I believe God forced him to add a few bits he probably would have preferred to leave out. And for Muslims, that's a very good thing. See, now, you have an escape clause. Your own book explicitly commands you to judge it by the Bible. The problem for Islam is that when you apply that test, the Qur'an fails miserably. Muhammad, though he affirmed the Christian scriptures, also opposed them, and violently at that. He was a false prophet, and a blasphemer. And tragically, he never repented of it. Therefore, he is eternally doomed.
But the scriptures Muhammad affirmed as divine revelations give you clear instructions for how not to join him in the unquenched fires of Hell. Put simply, believe. Believe in the Lord Jesus Christ, not as Muhammad preached Him, but as the Bible describes Him: The Lord of Heaven and Earth, crucified for sins, and risen as the firstborn among many brethren. All who confess Jesus as Lord, and believe He rose from the dead, will be saved. Therefore, do as Muhammad commanded. Judge by the scriptures of the Jews and the Christians, for you have no ground to stand upon if you do not.