Yahya bin Sa'id (may Allah have mercy on him) said: A man who had wounded a dhimmi was brought to Umar (may Allah be pleased with him), and he (may Allah be pleased with him) wanted to take retaliation from him. The Muslims said: This cannot be. Umar (may Allah be pleased with him) said: Then we will double the blood money against him; so the blood money was doubled. And Isma'il bin Abi Hakim said: I heard Umar bin Abd al-Aziz (may Allah have mercy on him) narrating to the people that a man from the dhimmis was deliberately killed in Syria, and Umar (may Allah be pleased with him) was in Syria at that time. When this reached him, he (may Allah be pleased with him) said: Now he too will be killed in retaliation. Abu Ubaydah bin al-Jarrah (may Allah be pleased with him) said: This cannot be. Umar (may Allah be pleased with him) prayed, then called Abu Ubaydah (may Allah be pleased with him) and asked: Why should I not kill him? Abu Ubaydah (may Allah be pleased with him) said: If the slain man had been (your) slave, would you still have killed him? Umar (may Allah be pleased with him) fell silent, and he ruled against him for a thousand dinars, imposing it severely.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15927