Sahih al-Bukhari 4870
Sahih al-Bukhari · Book 65: Prophetic Commentary on the Qur'an (Tafseer of the Prophet (pbuh)) · "And We have indeed made the Qur'an easy to understand and remember; then is there any one who will remember (or receive admonition)?" (V.54:17)
Narrated `Abdullah bin Masud:
حَدَّثَنَا مُسَدَّدٌ ، عَنْ يَحْيَى ، عَنْ شُعْبَةَ ، عَنْ أَبِي إِسْحَاقَ ، عَنِ الأَسْوَدِ ، عَنْ عَبْدِ اللَّهِ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم. أَنَّهُ كَانَ يَقْرَأُ {فَهَلْ مِنْ مُدَّكِرٍ} .
The Prophet (ﷺ) used to recite: "Fahal-min-Maddakir (then is there any that will receive admonition?")