Narrated Abu Said Al-Khudri:

The Prophet ﷺ said to his companions, "Is it difficult for any of you to recite one third of the Qur'an in one night?" This suggestion was difficult for them so they said, "Who among us has the power to do so, O Allah's Apostle?" Allah Apostle replied: " Allah (the) One, the Self-Sufficient Master Whom all creatures need.' (Surat Al-Ikhlas 112.1--to the End) is equal to one third of the Qur'an."

حَدَّثَنَا عُمَرُ بْنُ حَفْصٍ، حَدَّثَنَا أَبِي، حَدَّثَنَا الأَعْمَشُ، حَدَّثَنَا إِبْرَاهِيمُ، وَالضَّحَّاكُ الْمَشْرِقِيُّ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ، رضى الله عنه قَالَ قَالَ النَّبِيُّ ﷺ لأَصْحَابِهِ " أَيَعْجِزُ أَحَدُكُمْ أَنْ يَقْرَأَ ثُلُثَ الْقُرْآنِ فِي لَيْلَةٍ ". فَشَقَّ ذَلِكَ عَلَيْهِمْ وَقَالُوا أَيُّنَا يُطِيقُ ذَلِكَ يَا رَسُولَ اللَّهِ فَقَالَ " اللَّهُ الْوَاحِدُ الصَّمَدُ ثُلُثُ الْقُرْآنِ ". قَالَ أَبُو عَبْدِ اللَّهِ عَنْ إِبْرَاهِيمَ مُرْسَلٌ وَعَنِ الضَّحَّاكِ الْمَشْرِقِيِّ مُسْنَدٌ.