Abd al-Rahman bin al-Baylamani said: A man from among the dhimmis came to the Prophet (peace and blessings be upon him) and said: We had such-and-such an agreement with you. One of your men has killed one of our men. He (peace and blessings be upon him) said: "I have the greatest right to fulfil my covenant of protection." So he (peace and blessings be upon him) had that Muslim killed.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجنايات / 15919