Mukhtasar Bukhari

Narrated by Umm al-Mu'mineen Aisha Siddiqa (may Allah be pleased with her): When, on the day of the Battle of Uhud, the Prophet Muhammad (peace and blessings be upon him) had suffered what was destined for him and the polytheists had retreated, the Prophet (peace be upon him), fearing that they might return, said: "Who will go after these disbelievers?" Upon hearing this, seventy companions accepted the command of the Prophet (peace be upon him). (The narrator of the hadith, Urwah, says) Among them were Sayyiduna Abu Bakr and Sayyiduna Zubair (may Allah be pleased with them both).