It is narrated from Sayyidah Umm Salamah (may Allah be pleased with her); she said: I have not forgotten the mark on his (peace and blessings be upon him) chest on the day of the Battle of the Trench (al-Khandaq), while he (peace and blessings be upon him) was handing the bricks to the people and saying: "O Allah, the true good is the good of the Hereafter, so forgive the Ansar and the Muhajirun." Then when he (peace and blessings be upon him) saw him (that is, Sayyiduna Ammar (may Allah be pleased with him)), he said: "O son of Sumayyah, the rebellious group will kill you."
Hadith Referenceالمعجم الكبير للطبراني / مسند النساء / 20156