Surah Al Ankabut Tafseer

وَمَا كُنتَ تَتْلُو مِن قَبْلِهِ مِن كِتَابٍ وَلَا تَخُطُّهُ بِيَمِينِكَ

Neither did you read any book before it (this Qur'an) nor did you write any book with your right hand.

meaning, `you lived among your people for a long time before you brought this Qur'an. During this time you never read any book or wrote anything. Your people, as well as others all know that you are an unlettered man who does not read or write.'

This is how he was also described in the previous Scriptures, as Allah says:

الَّذِينَ يَتَّبِعُونَ الرَّسُولَ النَّبِىَّ الاُمِّىَّ الَّذِى يَجِدُونَهُ مَكْتُوبًا عِندَهُمْ فِى التَّوْرَاةِ وَالاِنجِيلِ يَأْمُرُهُم بِالْمَعْرُوفِ وَيَنْهَـهُمْ عَنِ الْمُنْكَرِ

Those who follow the Messenger, the Prophet, the unlettered about whom they find written with them in the Tawrah and the Injil, -- he commands them with good; and forbids them from evil. (7:157)

This is how the Messenger of Allah will remain until the Day of Resurrection, unable to write even one line or one letter. He used to have scribes who would write down the revelation for him, or would write letters from him to be sent to different places.

Allah's saying:

إِذًا لاَّرْتَابَ الْمُبْطِلُونَ

In that case, indeed, the followers of falsehood might have doubted.

means, `if you had been literate, some ignorant people would have doubted you. They would have said that you learned this from Books inherited from the Prophets which came before.'

Indeed, they did say that, even though they knew that he was unlettered and could not read or write.

وَقَالُواْ أَسَـطِيرُ الاٌّوَّلِينَ اكْتَتَبَهَا فَهِىَ تُمْلَى عَلَيْهِ بُكْرَةً وَأَصِيلً

And they say:"Tales of the ancients, which he has written down, and they are dictated to him morning and afternoon." (25:5)

Allah says:

قُلْ أَنزَلَهُ الَّذِى يَعْلَمُ السِّرَّ فِى السَّمَـوَتِ وَالاٌّرْضِ

Say:"It has been sent down by Him Who knows the secret of the heavens and the earth. (25:6)

And Allah says here