Musannaf Ibn Abi Shaybah 40650 — reports on Siffin

Abu Wa'il said: Abu Maysarah Amr bin Shurahbil, one of the best companions of Sayyiduna Abdullah (may Allah be pleased with him), saw in a dream that he said: "I entered Paradise and saw domes pitched there. I asked: 'Whose are these?' I was told: 'These belong to Dhu al-Kala' and Hawshab.' These two were with Sayyiduna Muawiyah (may Allah be pleased with him) in the Battle of Siffin and were martyred. I said: 'Where are Ammar and his companions?' I was told: 'They are in front of you.' I said: 'But these people killed one another; how then have they all come to Paradise?' I was told: 'When they met Allah, they found Him vast in forgiveness.' I said: 'What became of the people of al-Nahr?' I was told: 'They met with severity.'"