Al-Walid said :I asked Abu `Amr: What are they writing? He said: The sermon which he heard that day.
حَدَّثَنَا عَلِيُّ بْنُ سَهْلٍ الرَّمْلِيُّ، قَالَ حَدَّثَنَا الْوَلِيدُ، قَالَ قُلْتُ لأَبِي عَمْرٍو مَا يَكْتُبُوهُ قَالَ الْخُطْبَةَ الَّتِي سَمِعَهَا يَوْمَئِذٍ مِنْهُ .
AbuDaud
Knowledge (Kitab Al-Ilm) • Hadith 3650