﴿ لَّا يَمَسُّهُۥٓ إِلَّا ٱلْمُطَهَّرُونَ ﴾

“which none but the pure [of heart] can touch:”

(Which none toucheth) i.e. the Guarded Tablet (save the purified) from ritual impurities and sins, i.e. the angels; it is also said that this means: none acts upon the Qur'an except those who are given success,