from Anas bin Malik that the Messenger of Allah ﷺ said: "The rewards for my Ummah were displayed before me, even (the reward for) the dust that a man comes out of the Masjid with. The sins of my Ummah were displayed before me, and I have not seen a sin worse than a Surah or Ayah of the Qur'an which a man learned and then forgot."  

قَالَ رَسُولُ اللَّهِ ﷺ عُرِضَتْ عَلَىَّ أُجُورُ أُمَّتِي حَتَّى الْقَذَاةِ يُخْرِجُهَا الرَّجُلُ مِنَ الْمَسْجِدِ وَعُرِضَتْ عَلَىَّ ذُنُوبُ أَمَّتِي فَلَمْ أَرَ ذَنْبًا أَعْظَمَ مِنْ سُورَةٍ مِنَ الْقُرْآنِ أَوْ آيَةٍ أُوتِيهَا رَجُلٌ ثُمَّ نَسِيَهَا