Sahih Bukhari Volume 5, Book 64, Hadith 4114

حَدَّثَنَا الْمَكِّيُّ بْنُ إِبْرَاهِيمَ، حَدَّثَنَا هِشَامٌ، عَنْ يَحْيَى، عَنْ أَبِي سَلَمَةَ، عَنْ جَابِرِ بْنِ عَبْدِ اللَّهِ، أَنَّ عُمَرَ بْنَ الْخَطَّابِ ـ رضى الله عنه ـ جَاءَ يَوْمَ الْخَنْدَقِ بَعْدَ مَا غَرَبَتِ الشَّمْسُ جَعَلَ يَسُبُّ كُفَّارَ قُرَيْشٍ قَالَ يَا رَسُولَ اللَّهِ مَا كِدْتُ أَنْ أُصَلِّيَ حَتَّى كَادَتِ الشَّمْسُ أَنْ تَغْرُبَ‏.‏ قَالَ النَّبِيُّ صلى الله عليه وسلم ‏"‏ وَاللَّهِ مَا صَلَّيْتُهَا ‏"‏ فَنَزَلْنَا مَعَ النَّبِيِّ صلى الله عليه وسلم بُطْحَانَ، فَتَوَضَّأَ لِلصَّلاَةِ وَتَوَضَّأْنَا لَهَا، فَصَلَّى الْعَصْرَ بَعْدَ مَا غَرَبَتِ الشَّمْسُ، ثُمَّ صَلَّى بَعْدَهَا الْمَغْرِبَ‏

Narrated By Jabir bin 'Abdullah : Umar bin Al-Khattab came on the day of Al-Khandaq after the sun had set and he was abusing the infidels of Quraish saying, "O Allah's Apostle! I was unable to offer the ('Asr) prayer till the sun was about to set." The Prophet said, "By Allah, I have not offered this (i.e. 'Asr) prayer." So we came down along with the Prophet to Buthan where he performed ablution for the prayer and then we performed the ablution for it. Then he offered the 'Asr prayer after the sun had set, and after it he offered the Maghrib prayer.