Sunan al-Nasa'i
The Book of the Etiquette of Judges — Hadith #5415
أَخْبَرَنَا قُتَيْبَةُ، قَالَ حَدَّثَنَا أَبُو عَوَانَةَ، عَنْ عَبْدِ الْمَلِكِ بْنِ عُمَيْرٍ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ أَبِي بَكْرَةَ، قَالَ كَتَبَ أَبِي وَكَتَبْتُ لَهُ إِلَى عُبَيْدِ اللَّهِ بْنِ أَبِي بَكْرَةَ وَهُوَ قَاضِي سِجِسْتَانَ أَنْ لاَ، تَحْكُمَ بَيْنَ اثْنَيْنِ وَأَنْتَ غَضْبَانُ فَإِنِّي سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ
" لاَ يَحْكُمْ أَحَدٌ بَيْنَ اثْنَيْنِ وَهُوَ غَضْبَانُ " .
“My father wrote to ‘Ubaidullah bin Abi Bakrah – who was the judge of Sijistan – saying: ‘Do not pass judgment between two people when you are angry, for I heard the Messenger of Allah say: No one should pass judgment between two people when he is angry.'”
Chain of Narration (Isnad)