Yahya related to me from Malik from Abdullah ibn Abi Bakr ibn Hazm that in a letter that the Messenger of Allah ﷺ sent to Amr ibn Hazm it said that no-one should touch the Qur'an unless he was pure.

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ عَبْدِ اللَّهِ بْنِ أَبِي بَكْرِ بْنِ حَزْمٍ، . أَنَّ فِي الْكِتَابِ الَّذِي، كَتَبَهُ رَسُولُ اللَّهِ ﷺ لِعَمْرِو بْنِ حَزْمٍ " أَنْ لاَ يَمَسَّ الْقُرْآنَ إِلاَّ طَاهِرٌ " .