حَدَّثَنَا يَحْيَى بْنُ حَسَّانَ، حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ مُسْلِمٍ، عَنْ عَبْدِ اللَّهِ بْنِ دِينَارٍ، قَالَ: كَتَبَ عُمَرُ بْنُ عَبْدِ الْعَزِيزِ إِلَى أَهْلِ الْمَدِينَةِ: "أَنْ انْظُرُوا حَدِيثَ رَسُولِ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ فَاكْتُبُوهُ، فَإِنِّي قَدْ خِفْتُ دُرُوسَ الْعِلْمِ وَذَهَابَ أَهْلِهِ".
Abdullah bin Dinar said that Umar bin Abdul Aziz, may Allah have mercy on him, wrote to the people of Madinah to search for the hadith of the Messenger of Allah, peace and blessings be upon him, and write it down. He said, "I fear the disappearance of knowledge and the loss or departure of the people of knowledge."