Musnad Ahmad 31:653

Yazid and Hajjaj narrated to us, they said: Ibn Abi Dhi’b informed us, from al-Maqburi, from ‘Abd al-Rahman ibn Abi Sa’id al-Khudri, from his father, who said: We were detained on the day of the Trench until a portion of the night had passed, until we were spared [from the fighting]. That is the saying of Allah: "And Allah spared the believers the fighting, and Allah is All-Powerful, Exalted in Might" [Al-Ahzab: 25]. He said: The Messenger of Allah (peace and blessings of Allah be upon him) called Bilal, and he commanded him, so he performed the iqamah, and he [the Prophet] prayed Dhuhr, and he performed it well just as he used to pray it in its time. Then he performed the iqamah for ‘Asr, and he prayed it likewise. Then he performed the iqamah for Maghrib, and he prayed it likewise. Then he performed the iqamah for ‘Isha, and he prayed it likewise. And that was before the [revelation regarding] the prayer of fear was sent down. Hajjaj said regarding the prayer of fear: "But if you fear, then [pray] on foot or riding" [Al-Baqarah: 239].