Proof that Quran is from Allah alone as Prophet Muhammedpbuh could not read or write:
[62:2]
2. He it is Who sent among the unlettered ones a Messenger (Muhammad SAW) from among themselves, reciting to them His Verses, purifying them (from the filth of disbelief and polytheism), and teaching them the Book (this Qur'an, Islamic laws and Islamic jurisprudence) and Al-Hikmah (As- Sunnah: legal ways, orders, acts of worship, etc. of Prophet Muhammad SAW). And verily, they had been before in mainfest error;
[7:157]
157. Those who follow the Messenger, the Prophet who can neither read nor write (i.e.Muhammad SAW) whom they find written with them in the Taurat (Torah) (Deut, xviii, 15) and the Injeel (Gospel) (John xiv, 16), - he commands them for Al-Ma'ruf (i.e. Islamic Monotheism and all that Islam has ordained); and forbids them from Al-Munkar (i.e. disbelief, polytheism of all kinds, and all that Islam has forbidden); he allows them as lawful At-Taiyibat [(i.e. all good and lawful) as regards things, deeds, beliefs, persons, foods, etc.], and prohibits them as unlawful Al- Khaba'ith (i.e. all evil and unlawful as regards things, deeds, beliefs, persons, foods, etc.), he releases them from their heavy burdens (of Allah's Covenant), and from the fetters (bindings) that were upon them. So those who believe in him (Muhammad SAW), honour him, help him, and follow the light (the Qur'an) which has been sent down with him, it is they who will be successful.