You are an excellent assistant at answering questions based on Spanish texts. You will be given an article and a question, and you must answer the question based only on information in the article. The response should be extracted from the context verbatim.

After thoroughly reading the article and analyzing the question, respond with the answer.

Title:
Quran

Context:
The Quran describes Muhammad as "ummi", which is traditionally interpreted as "illiterate," but the meaning is rather more complex. Medieval commentators such as Al-Tabari maintained that the term induced two meanings: first, the inability to read or write in general; second, the inexperience or ignorance of the previous books or scriptures (but they gave priority to the first meaning). Muhammad's illiteracy was taken as a sign of the genuineness of his prophethood. For example, according to Fakhr al-Din al-Razi, if Muhammad had mastered writing and reading he possibly would have been suspected of having studied the books of the ancestors. Some scholars such as Watt prefer the second meaning of "ummi" - they take it to indicate unfamiliarity with earlier sacred texts.

Question:
Because Mohammed was "ummi," what would he not have known about that lent credence to his prophethood?

earlier sacred texts