Musannaf Ibn Abi Shayba 37:595

Ghundar narrated to us, from Shu'bah, from 'Asim, who said: I heard Abu Wa'il saying: When 'Uthman was killed, Abu Musa said: "Indeed, this tribulation is a destructive tribulation, like a disease of the abdomen; we do not know from where it comes. It comes to you from your place of security, and it leaves the forbearing man as if he were a stranger (lit: son of yesterday). Sever your ties of kinship and break your spears."