"My father wrote to 'Ubaidullah bin Abi Bakrah who was a judge: "Do not pass a judgement between two people while you are angry, for indeed I heard the Messenger of Allah ﷺ saying: 'The judge should not judge between two people while he is angry.'"  

أَنْ لاَ تَحْكُمْ بَيْنَ اثْنَيْنِ وَأَنْتَ غَضْبَانُ فَإِنِّي سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ لاَ يَحْكُمُ الْحَاكِمُ بَيْنَ اثْنَيْنِ وَهُوَ غَضْبَانُ