Sahih Bukhari Volume 1, Book 10, Hadith Number 572

Narated By Jabir : Umar came cursing the disbelievers (of Quraish) on the day of Al-Khandaq (the battle of Trench) and said, “I could not offer the ‘Asr prayer till the sun had set. Then we went to Buthan and he offered the (‘Asr) prayer after sunset and then he offered the Maghrib prayer.