Prophet Muhammad was illiterate
He could not read or write. He never lived outside Makkah or sought foreign knowledge. Muslims believe that Muhammad¤ did not write or author the “Quran”. He conveyed it (as Allah's Message to humanity) letter by letter and word by word without rephrasing any part of it with his own words.
Muhammad’s sayings and teachings were not mixed with the Quran:
They were collected in books which are called “Hadith or the Sunnah of the Prophet”, which means his teachings, way of life and explanation of the Book (The Quran).