It is narrated from Hazrat Abu Saeed (may Allah be pleased with him) that a person better than me narrated to me: When the Messenger of Allah (peace and blessings be upon him) began digging the trench, he would dust off the head of Hazrat Ammar (may Allah be pleased with him) and would say, "O son of Sumayyah! Alas, a rebellious group will martyr you."