Musnad Ahmad 31:210

Yahya narrated to us, Ibn Abi Dhi’b narrated to us, Sa’id ibn Abi Sa’id narrated to us, from ‘Abd al-Rahman ibn Abi Sa’id, from his father, who said: We were detained on the day of the Trench from the prayers until it was well into the night after Maghrib. That was before what was revealed regarding fighting was revealed. When we were spared the fighting—and that is His saying: "And Allah spared the believers the fighting, and Allah is ever Powerful, Exalted in Might" [Al-Ahzab: 25]—the Prophet, peace and blessings of Allah be upon him, commanded Bilal, so he performed the iqamah for Dhuhr, and he prayed it as he would pray it in its time. Then he performed the iqamah for ‘Asr, and he prayed it as he would pray it in its time. Then he performed the iqamah for Maghrib, and he prayed it as he would pray it in its time.