(As for those who heard the call of Allah and His messenger…) [3:172].
Ahmad ibn Ibrahim al-Muqri' informed us> Shu'ayb ibn Muhammad> Makki ibn 'Abdan> Abu'l-Azhar> Rawh> Abu Yunus al-Qushayri> 'Amr ibn Dinar who reported that the Messenger of Allah, Allah bless him and give him peace, made a general call to arms after the Battle of Uhud, when the idolaters had departed, and seventy men answered his call and he went after the retreating army of the idolaters. On his way back to Mecca, Abu Sufyan met a caravan from Khuza'ah and he said to them: “If you see Muhammad coming after me, tell him that we are in great numbers”. When the Prophet, Allah bless him and give him peace, met them and asked them about Abu Sufyan, they said to him: “We saw him with a huge army whereas yours is very small; you will not be safe with him”. But the Messenger of Allah, Allah bless him and give him peace, refused to listen to them and went after him. But Abu Sufyan went ahead of him and entered Mecca. Allah, exalted is He, then revealed (As for those who heard the call of Allah and His messenger) up to His saying (Fear them not; fear Me, if ye are true believers) [3:175].
'Amr ibn Abi 'Amr informed us> Muhammad ibn Makki> Muhammad ibn Yusuf> Muhammad ibn Isma'il> Muhammad> Abu Mu'awiyah> Hisham ibn 'Urwah> his father> 'A'ishah who said to 'Urwah [ibn al-Zubayr] regarding Allah's saying (As for those who heard the call of Allah and His messenger): “O my nephew! Your father, al-Zubayr, and grandfather, Abu Bakr, were among them. When the Messenger of Allah, Allah bless him and give him peace, suffered that which he suffered at the Battle of Uhud, and after the idolaters had left, he feared their return, and so he said: 'Who will go after them?' He selected seventy men from amongst them, among whom were Abu Bakr and al-Zubayr”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou