Musannaf Ibn Abi Shayba 18:1145

Abu Bakr narrated to us, he said: Muhammad ibn Ubayd narrated to us, from Muhammad ibn Ishaq, he said: Makhul narrated to me, he said: When Umar came to us in Jerusalem, Ubadah ibn al-Samit gave a man from the people of the dhimma his mount to hold, but he refused him, so he struck him, causing a *mudihah* (a wound that exposes the bone). Then he entered the mosque. When Umar came out, the Nabataean shouted to Umar. Umar said: "Who is the owner of this?" Ubadah said: "I am the owner of this." He said: "What did you intend by this?" He said: "I gave him my mount to hold, and he refused, and I am a man who is quick-tempered." He said: "If not, then sit for retaliation (*qisas*)." Zayd ibn Thabit said to him: "You would not retaliate against your servant for your brother?" He said: "Nay, by Allah, if I refrain from retaliation for your sake, I will burden you with the blood money; give him its blood money twice."