Musnad Ahmad 5:704

Abdullah narrated to us, Ismail Abu Ma'mar narrated to me, Ibn 'Ulayyah narrated to us, from Yunus, from al-Hasan, from Qays ibn 'Abbad, who said: I said to Ali: "What do you think about this march of yours? Is it a covenant that the Messenger of Allah, peace and blessings of Allah be upon him, made with you, or is it an opinion you have formed?" He said: "What do you want with this?" I said: "Our religion, our religion." He said: "The Messenger of Allah, peace and blessings of Allah be upon him, did not make any covenant with me regarding it, but it is an opinion I have formed."