Hisham bin Urwah narrates from his father that Sayyidah Aishah (may Allah be pleased with her) said to him: "O son of my sister! Your two fathers, al-Zubayr and Abu Bakr (may Allah be pleased with them both), were among those who responded to Allah and His Messenger (peace and blessings be upon him) after injury had struck them [Surah Al Imran: 172]." She said: When the polytheists turned back from Uhud, and the Prophet (peace and blessings be upon him) and his Companions had suffered what they suffered, he (peace and blessings be upon him) feared that they would return, so he (peace and blessings be upon him) said: "Who will volunteer to pursue them, so that they know that we still have strength?" So Abu Bakr and al-Zubayr (may Allah be pleased with them both) were among the seventy men who went after them. They heard news of them and returned with blessing and grace from Allah. She said: They did not meet the enemy.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب قسم الفيء والغنيمة / 13088