Musnad Ahmad 30:2518

Yahya narrated to us, from Malik, who said: Al-Zuhri narrated to me, from Sa'id ibn al-Musayyib, from Abu Hurayrah, who said: "The Messenger of Allah (may Allah bless him and grant him peace) announced to us the death of the Negus on the day he died. He went out to the prayer ground (musalla), lined up his companions behind him, and performed four takbirs over him."