On the day of Al-Khandaq (the trench), ʿUmar bin Al-Khattab went to the Prophet ﷺ and said, "O Messenger of Allah ﷺ! By Allah, I could not pray (the ʿAsr) till the sun had set." ʿUmar told this to the Prophet at the time when a fasting person had done Iftar (taken his meals). The Prophet ﷺ then went to Buthan and I was with him. He performed ablution and offered the ʿAsr prayer after the sun had set and then the Maghrib prayer.  

أَنَّ النَّبِيَّ ﷺ جَاءَهُ عُمَرُ بْنُ الْخَطَّابِ يَوْمَ الْخَنْدَقِ فَقَالَ يَا رَسُولَ اللَّهِ وَاللَّهِ مَا كِدْتُ أَنْ أُصَلِّيَ حَتَّى كَادَتِ الشَّمْسُ تَغْرُبُ وَذَلِكَ بَعْدَ مَا أَفْطَرَ الصَّائِمُ فَقَالَ النَّبِيُّ ﷺ وَاللَّهِ مَا صَلَّيْتُهَا فَنَزَلَ النَّبِيُّ ﷺ إِلَى بُطْحَانَ وَأَنَا مَعَهُ فَتَوَضَّأَ ثُمَّ صَلَّى يَعْنِي الْعَصْرَ بَعْدَ مَا غَرَبَتِ الشَّمْسُ ثُمَّ صَلَّى بَعْدَهَا الْمَغْرِبَ