Musnad Ahmad 1007:93

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Abu Maslamah, who said: I heard Abu Nadrah narrating from Abu Sa'id al-Khudri, who said: One who is better than me informed me that the Messenger of Allah (may Allah bless him and grant him peace) said to Ammar when he was digging the trench, while he was wiping his head: "Woe to the son of Sumayyah, the rebellious faction will kill you."