Allah tells us about His Book, which falsehood cannot approach from before or behind it, sent down by the All-Wise, Worthy of all praise. He states that it has been brought down by the trustworthy Ruh (i.e., Jibril) who is helped by Allah,
وَمَا تَنَزَّلَتْ بِهِ الشَّيَـطِينُ
(And it is not the Shayatin who have brought it down.) Then He tells us that it could not be the case for three reasons that the Shayatin brought it down. One is that it would not suit them, i.e., they have no desire to do so and they do not want to, because their nature is to corrupt and misguide people, but this contains words enjoining what is right and forbidding what is evil, and light, guidance and mighty proofs. There is a big difference between this and the Shayatin, Allah says:
وَمَا يَنبَغِى لَهُمْ
(Neither would it suit them)
وَمَا يَسْتَطِيعُونَ
(nor are they able.) meaning, even if they wanted to, they could not do it. Allah says:
لَوْ أَنزَلْنَا هَـذَا الْقُرْءَانَ عَلَى جَبَلٍ لَّرَأَيْتَهُ خَـشِعاً مُّتَصَدِّعاً مِّنْ خَشْيَةِ اللَّهِ
(Had We sent down this Qur'an on a mountain, you would surely have seen it humbling itself and rent asunder by the fear of Allah) (59:21). Then Allah explains that even if they wanted to and were able to bear it and convey it, they still would not be able to achieve that, because they were prevented from hearing the Qur'an when it was brought down, for the heavens were filled with guardians and shooting stars at the time when the Qur'an was being revealed to the Messenger of Allah ﷺ, so none of the Shayatin could hear even one letter of it, lest there be any confusion in the matter. This is a part of Allah's mercy towards His servants, protection of His Laws, and support for His Book and His Messenger . Allah says:
إِنَّهُمْ عَنِ السَّمْعِ لَمَعْزُولُونَ
(Verily, they have been removed far from hearing it.) This is like what Allah tells us about the Jinn:
وَأَنَّا لَمَسْنَا السَّمَآءَ فَوَجَدْنَـهَا مُلِئَتْ حَرَساً شَدِيداً وَشُهُباً - وَأَنَّا كُنَّا نَقْعُدُ مِنْهَا مَقَـعِدَ لِلسَّمْعِ فَمَن يَسْتَمِعِ الاٌّنَ يَجِدْ لَهُ شِهَاباً رَّصَداً
(And we have sought to reach the heaven; but found it filled with stern guards and flaming fires. And verily, we used to sit there in stations, to (steal) a hearing, but any who listens now will find a flaming fire watching him in ambush.) until;
أَمْ أَرَادَ بِهِمْ رَبُّهُمْ رَشَداً
(or whether their Lord intends for them a right path) 72:8-10.