Musannaf Ibn Abi Shayba 3:2378

Waki' narrated to us, from Ali ibn al-Mubarak, from Yahya, from Abu Salamah, from Jabir, who said: Umar came on the day of the Trench and began to curse the disbelievers of Quraysh and said: "O Messenger of Allah, I did not pray the Asr prayer until the sun had almost set." The Messenger of Allah (peace be upon him) said: "And I, by Allah, have not prayed it yet." So he descended and performed ablution, then he prayed the Asr prayer after the sun had set, then he prayed the Maghrib prayer after he had prayed the Asr prayer.