Mishkat al-Masabih
Prayer — Hadith #671
وَعَنْ أَنَسِ بْنِ مَالِكٍ قَالَ: قَالَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسلم: «عُرِضَتْ عَلَيَّ أُجُورُ أُمَّتِي حَتَّى الْقَذَاةُ يُخْرِجُهَا الرَّجُلُ مِنَ الْمَسْجِدِ وَعُرِضَتْ عَلَيَّ ذُنُوبُ أُمَّتِي فَلَمْ أَرَ ذَنْبًا أَعْظَمَ مِنْ سُورَةٍ مِنَ الْقُرْآنِ أَوْ آيَةٍ أُوتِيهَا رَجُلٌ ثُمَّ نَسِيَهَا» . رَوَاهُ التِّرْمِذِيُّ وَأَبُو دَاوُد
He also reported God’s Messenger as saying, “The rewards of my people were placed before me, even and the sins of my people were placed before me, and I saw no sin greater than that a man should memorise a sura or verse of the Qur’an, then forget it.”*
* Cf. Al-Qur’an, 20:126.
Tirmidhi and Abu Dawud transmitted it.