Musnad Ahmad 30:3721

Rawh narrated to us, Muhammad ibn Abi Hafsah narrated to us, from al-Zuhri, from Sa’id ibn al-Musayyib and Abu Salamah ibn ‘Abd al-Rahman, from Abu Hurayrah, that the Messenger of Allah (ﷺ) announced the death of the Negus to his companions, then said: "Seek forgiveness for him." Then he went out with his companions to the prayer ground, then he stood and prayed over him as one prays over the funeral.