The Quran confirms the Arabs were not illiterate

The longest verse in the Quran commands the recipients of the Quran to write down financial transactions.

[2:282] O you who believe, when you transact a loan for any period, you shall write it down. An impartial scribe shall do the writing. No scribe shall refuse to perform this service, according to GOD's teachings. He shall write, while the debtor dictates the terms. He shall observe GOD his Lord and never cheat. If the debtor is mentally incapable, or helpless, or cannot dictate, his guardian shall dictate equitably. Two men shall serve as witnesses; if not two men, then a man and two women whose testimony is acceptable to all. Thus, if one woman becomes biased, the other will remind her. It is the obligation of the witnesses to testify when called upon to do so. Do not tire of writing the details, no matter how long, including the time of repayment. This is equitable in the sight of GOD, assures better witnessing, and eliminates any doubts you may have. Business transactions that you execute on the spot, need not be recorded, but have them witnessed. No scribe or witness shall be harmed on account of his services. If you harm them, it would be wickedness on your part. You shall observe GOD, and GOD will teach you. GOD is Omniscient.

(٢٨٢) يَـٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِذَا تَدَايَنتُم بِدَيْنٍ إِلَىٰٓ أَجَلٍ مُّسَمًّى فَٱكْتُبُوهُ وَلْيَكْتُب بَّيْنَكُمْ كَاتِبٌۢ بِٱلْعَدْلِ وَلَا يَأْبَ كَاتِبٌ أَن يَكْتُبَ كَمَا عَلَّمَهُ ٱللَّهُ فَلْيَكْتُبْ وَلْيُمْلِلِ ٱلَّذِى عَلَيْهِ ٱلْحَقُّ وَلْيَتَّقِ ٱللَّهَ رَبَّهُۥ وَلَا يَبْخَسْ مِنْهُ شَيْـًٔا فَإِن كَانَ ٱلَّذِى عَلَيْهِ ٱلْحَقُّ سَفِيهًا أَوْ ضَعِيفًا أَوْ لَا يَسْتَطِيعُ أَن يُمِلَّ هُوَ فَلْيُمْلِلْ وَلِيُّهُۥ بِٱلْعَدْلِ وَٱسْتَشْهِدُوا۟ شَهِيدَيْنِ مِن رِّجَالِكُمْ فَإِن لَّمْ يَكُونَا رَجُلَيْنِ فَرَجُلٌ وَٱمْرَأَتَانِ مِمَّن تَرْضَوْنَ مِنَ ٱلشُّهَدَآءِ أَن تَضِلَّ إِحْدَىٰهُمَا فَتُذَكِّرَ إِحْدَىٰهُمَا ٱلْأُخْرَىٰ وَلَا يَأْبَ ٱلشُّهَدَآءُ إِذَا مَا دُعُوا۟ وَلَا تَسْـَٔمُوٓا۟ أَن تَكْتُبُوهُ صَغِيرًا أَوْ كَبِيرًا إِلَىٰٓ أَجَلِهِۦ ذَٰلِكُمْ أَقْسَطُ عِندَ ٱللَّهِ وَأَقْوَمُ لِلشَّهَـٰدَةِ وَأَدْنَىٰٓ أَلَّا تَرْتَابُوٓا۟ إِلَّآ أَن تَكُونَ تِجَـٰرَةً حَاضِرَةً تُدِيرُونَهَا بَيْنَكُمْ فَلَيْسَ عَلَيْكُمْ جُنَاحٌ أَلَّا تَكْتُبُوهَا وَأَشْهِدُوٓا۟ إِذَا تَبَايَعْتُمْ وَلَا يُضَآرَّ كَاتِبٌ وَلَا شَهِيدٌ وَإِن تَفْعَلُوا۟ فَإِنَّهُۥ فُسُوقٌۢ بِكُمْ وَٱتَّقُوا۟ ٱللَّهَ وَيُعَلِّمُكُمُ ٱللَّهُ وَٱللَّهُ بِكُلِّ شَىْءٍ عَلِيمٌ

walā	وَلَا	And not
tasamū	تَسْـَٔمُوٓا۟	you [all] tire
an	أَن	that
taktubūhu	تَكْتُبُوهُ	you [all] write it
ṣaghīran	صَغِيرًا	small
aw	أَوْ	or
kabīran	كَبِيرًا	large