Yahya related to me from Malik from Abd al-Malik ibn Qurayr fromMuhammad ibn Sirin that a man came to Umar ibn al-Khattab and said, "Iwas racing a friend on horseback towards a narrow mountain trail andwe killed a gazelle accidently and we were in ihram. What is youropinion?" Umar said to a man by his side, "Come, so that you and I maymake an assessment." They decided on a female goat for him, and theman turned away saying, "This amir al-muminin cannot even make anassessment in the case of a gazelle until he calls a man to decidewith him." Umar overheard the man's words and called him and askedhim, "Do you recite surat al-Ma'ida?" and he said, "No." He said,"Then do you recognize this man who has taken the decision with me?"and he said, "No." He said, "If you had told me that you did recitesurat al-Ma'ida, I would have dealt you a blow." Then he said, "Allahthe Blessed, the Exalted says in His Book, 'as shall be judged by twomen of justice among you, a sacrificial animal to reach the Kaba'(Sura 5 ayat 95), and this is Abd ar-Rahman ibn Awf."
USC-MSA web (English) reference: Book 20, Hadith 240
Arabic reference: Book 20, Hadith 938