That he saw Messenger of Allah ﷺ cutting a piece of mutton from its shoulder part he was carrying in his hand. When he was called for prayer, he put it down and the knife with which he was cutting it. Then he stood up and offered the prayer without performing new ablution.  

أَخْبَرَهُ أَنَّهُ رَأَى رَسُولَ اللَّهِ ﷺ يَحْتَزُّ مِنْ كَتِفِ شَاةٍ فِي يَدِهِ فَدُعِيَ إِلَى الصَّلاَةِ فَأَلْقَاهَا وَالسِّكِّينَ الَّتِي كَانَ يَحْتَزُّ بِهَا ثُمَّ قَامَ فَصَلَّى وَلَمْ يَتَوَضَّأْ  

The Prophet ﷺ said, If supper is served and the Iqama for (Isha) prayer is proclaimed, start with you supper first."  

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا وُضِعَ الْعَشَاءُ وَأُقِيمَتِ الصَّلاَةُ فَابْدَءُوا بِالْعَشَاءِ  

Once Ibn Umar was taking his supper while he was listening to the recitation of (Quran by) the Imam (in the Isha prayer).  

عَنِ النَّبِيِّ ﷺ نَحْوَهُ وَعَنْ أَيُّوبَ عَنْ نَافِعٍ عَنِ ابْنِ عُمَرَ أَنَّهُ تَعَشَّى مَرَّةً وَهْوَ يَسْمَعُ قِرَاءَةَ الإِمَامِ  

The Prophet ﷺ said, "If the Iqama for (ʿIsha') prayer is proclaimed and supper is served, take your supper first."  

عَنِ النَّبِيِّ ﷺ قَالَ إِذَا أُقِيمَتِ الصَّلاَةُ وَحَضَرَ الْعَشَاءُ فَابْدَءُوا بِالْعَشَاءِ قَالَ وُهَيْبٌ وَيَحْيَى بْنُ سَعِيدٍ عَنْ هِشَامٍ إِذَا وُضِعَ الْعَشَاءُ