Musannaf Ibn Abi Shayba 29:192

Ghundar narrated to us, from Shu'bah, from Iyas ibn Mu'awiyah, who said: I sat with Sa'id ibn al-Musayyib. He said to me: "From whom are you?" I said: "From Muzaynah." He said: "I truly remember the day Umar ibn al-Khattab announced the death of al-Nu'man from the pulpit."