Al-Lu'lu Wal-Marjan 366 — The Book of Mosques and Places of Worship.

Jabir bin `Abdullah Narrated from:

On the day of Al-Khandaq (the battle of Trench), ‘Umar bin Al-Khattab رضى الله عنه came cursing the disbelievers of Quraish after the sun had set and said, “O Allâh’s Messenger! I could not offer the ‘Asr prayer till the sun had set.” The Prophet صلى الله عليه وسلم said, “By Allâh! I, too, have not offered the Salât (prayer).” So we turned toward Buthan, and the Prophet صلى الله عليه وسلم performed ablution and we too performed ablution and offered the ‘Asr prayer after the sun had set, and then he offered the Maghrib prayer. ( Sahîh Al-Bukhârî, Hadîth No. 570, Vol. 1)