Sahih Bukhari Volume 5, Book 64, Hadith 4079

حَدَّثَنَا مُحَمَّدٌ، حَدَّثَنَا أَبُو مُعَاوِيَةَ، عَنْ هِشَامٍ، عَنْ أَبِيهِ، عَنْ عَائِشَةَ ـ رضى الله عنها ‏{‏الَّذِينَ اسْتَجَابُوا لِلَّهِ وَالرَّسُولِ مِنْ بَعْدِ مَا أَصَابَهُمُ الْقَرْحُ لِلَّذِينَ أَحْسَنُوا مِنْهُمْ وَاتَّقَوْا أَجْرٌ عَظِيمٌ‏}‏ قَالَتْ لِعُرْوَةَ يَا ابْنَ أُخْتِي كَانَ أَبُوكَ مِنْهُمُ الزُّبَيْرُ وَأَبُو بَكْرٍ، لَمَّا أَصَابَ رَسُولَ اللَّهِ صلى الله عليه وسلم مَا أَصَابَ يَوْمَ أُحُدٍ، وَانْصَرَفَ عَنْهُ الْمُشْرِكُونَ خَافَ أَنْ يَرْجِعُوا قَالَ ‏"‏ مَنْ يَذْهَبُ فِي إِثْرِهِمْ ‏"‏‏.‏ فَانْتَدَبَ مِنْهُمْ سَبْعُونَ رَجُلاً، قَالَ كَانَ فِيهِمْ أَبُو بَكْرٍ وَالزُّبَيْرُ‏

Narrated By 'Aisha : Regarding the Holy Verse: "Those who responded (To the call) of Allah And the Apostle (Muhammad), After being wounded, For those of them Who did good deeds And refrained from wrong, there is a great reward." (3.172) She said to 'Urwa, "O my nephew! Your father, Az-Zubair and Abu Bakr were amongst them (i.e. those who responded to the call of Allah and the Apostle on the day (of the battle of Uhud). When Allah's Apostle, suffered what he suffered on the day of Uhud and the pagans left, the Prophet was afraid that they might return. So he said, 'Who will go on their (i.e. pagans') track?' He then selected seventy men from amongst them (for this purpose)." (The sub-narrator added, "Abu Bakr and Az-Zubair were amongst them.")