During the battle of Siffin Amir al-mu'minin heard some of his men abusing the Syrians, then he said:
I dislike you starting to abuse them, but if you describe their deeds and recount their situations that would be a better mode of speaking and a more convincing way of arguing. Instead of abusing them you should say, "O Allah! Save our blood and their blood, produce reconciliation between us and them, and lead them out of their misguidance so that he who is ignorant of the truth may know it, and he who inclines towards rebellion and revolt may turn away from it."
(1) Al-Dinawari, al-'Akhbar, 155;
(2) Nasr, Siffin, 103;
(3) Sibt ibn al-Jawzi, Tadhkirah, 154.