Sahih Muslim | Book 18 | Hadith Number 4264

Narrated by Abd al-Rabmin b. Abu Bakra
Abd al-Rabmin b. Abu Bakra reported: My father dictated (and I wrote for him) to Ubaidullah b. Abu Bakra while he was the judge of Sijistan: Do not judge between two persons when you are angry, for I have heard Allah's Messenger (may peace be upon him) as saying: None of you should judge between two persons when he is angry.