It is narrated from Jabir bin Abdullah (may Allah be pleased with him) that on the day of the Trench (Khandaq), Umar (may Allah be pleased with him) came to the Messenger of Allah (peace and blessings be upon him) and began to revile the disbelievers, and said: "O Messenger of Allah! I prayed the Asr prayer only when the sun was about to set." He (peace and blessings be upon him) said: "By Allah! I have not been able to pray it even until sunset." Jabir bin Abdullah (may Allah be pleased with him) says: Then we went down to a place called Buthan; he (peace and blessings be upon him) performed ablution and prayed Asr after sunset, and then prayed Maghrib after it.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3186