Thirty sons of the Companions (may Allah be pleased with them) narrate from their fathers, who narrate from the Messenger of Allah (peace and blessings be upon him), that he (peace and blessings be upon him) said: "Whoever wrongs a non-Muslim under protection (dhimmi), disparages him, burdens him beyond his capacity, or takes anything from him without his consent, I will plead on his behalf on the Day of Resurrection." Pointing towards his chest, he (peace and blessings be upon him) said: "Beware! Whoever kills a protected non-Muslim under covenant, Allah Almighty has forbidden to him even the fragrance of Paradise, although its fragrance can be perceived from a distance of seventy years' travel."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18731