Musannaf Ibn Abi Shaybah 32642 — Reports on talk about rulers

Umayr bin Sa'd said: When Sayyiduna Ali (may Allah be pleased with him) returned from the Battle of the Camel and began preparing for Siffin, the tribe of al-Nakha' gathered and came to al-Ashtar. He asked: "Is there anyone in this house other than people of the tribe of al-Nakha'?" They answered in the negative. He said: "Indeed, this Ummah deliberately went for its best man and killed him. We advanced on the people of Basrah, over whom we had the right of the pledge of allegiance, and we were given help through their breaking of their pledge. You will soon march on the people of Syria, over whom you have no right of the pledge of allegiance, so let every man look and think carefully about where he will use his sword."