Musannaf Ibn Abi Shaybah 40680 — reports on Siffin

Abdullah bin Salamah said: I saw Sayyiduna Ammar (may Allah be pleased with him) in the Battle of Siffin. He was a very old man, dark-complexioned and tall; his hand was trembling and there was a spear in his hand. He was saying: "By the One in whose hand is my soul, even if the enemy were to strike us and crush us utterly, I would still be certain that our cause of setting things right is on the truth and that those people are on falsehood."