Musannaf Ibn Abi Shaybah 40674 — reports on Siffin

Sayyiduna Abdullah bin Amr (may Allah be pleased with him) said: When the people withdrew their hands from fighting at Siffin, Sayyiduna Amr bin al-As (may Allah be pleased with him) recited these verses: War has flared up, and I have readied for it a brave horse of noble breed. It joins one run to another, and when the horses tire of running it races on. It is sturdy, its girth the greatest part of it, and when it is wet with water it bursts forward. After this, Sayyiduna Abdullah bin Amr (may Allah be pleased with him) recited verses: If Jumal had witnessed my stand and my presence at Siffin on a day that turned the locks of hair white! That was the evening when the people of Iraq came like spring clouds lifted by the south winds. At that time our ranks were surging like the waves of the sea. Their mill turned and our mill turned through the height of the day, and shoulders did not turn away. Whenever I said they had fled, a group of them would suddenly come and attack. They would say to us: "Pledge allegiance at the hand of Sayyiduna Ali (may Allah be pleased with him)," and we would say: "Rather, we will fight."