Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Hisham bin Urwah that Hazrat Ibn Zubair used to attack them until he would drive them out from the doors, and he used to say, "If my opponent is alone, then I am sufficient for him," and he would also recite poetry: "And our wounds do not bleed upon our heels... rather, blood drips upon our feet." (The meaning is that we fight facing the enemy and do not turn our backs and flee.)