سنن النسائي

It was narrated that 'Abdur-Rahman bin Abi Bakrah said: "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 (ﷺ) [SAW] say: No one should pass judgment between two people when he is angry.'"