From Sahih Muslim (Hadith 4636):
It has been narrated through a different chain of transmitters on the authority of Abu Wa'il who said:I heard Sahl b. Hunaif say at Siffin: Blame (the hollowness) of your views about your religion. I thought to myself on the day of Abu Jandal that if I could turn down the order of the Messenger of Allah (ﷺ), I would. The situation was so difficult that if we mended it at one place, it was rent at another
Reference: Muslim 4636