Surah Al-'Ankabut 29:48

وَمَا كُنتَ تَتْلُوا۟ مِن قَبْلِهِۦ مِن كِتَـٰبٍ وَلَا تَخُطُّهُۥ بِيَمِينِكَ ۖ إِذًا لَّٱرْتَابَ ٱلْمُبْطِلُونَ

And you did not recite before it any scripture, nor did you inscribe one with your right hand. Then [i.e., otherwise] the falsifiers would have had [cause for] doubt.

Translation: Saheeh International

Tafsir

And you did not use to recite before this namely before the Qur’ān any other Book nor did you write it with your right hand for had you been reciting something and writing then those who follow falsehood the Jews would have had doubts about you and would have said ‘What the Torah states is that he will be unlettered …

Excerpt from Tafsir al-Jalalayn, commentary on 29:48, via Quran.com. The reader has the full commentary and 9 more tafsirs.