Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) said: "Whoever kills a protected non-Muslim (mu'ahad) without right will not even smell the fragrance of Paradise, though its fragrance can be found from a distance of forty years."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16482
Abu Bakrah (may Allah be pleased with him) narrated from the Prophet (peace and blessings be upon him): "The fragrance of Paradise can be perceived from a distance of 100 years, and whoever kills a protected non-Muslim, Allah forbids him even the fragrance of Paradise." Abu Bakrah (may Allah be pleased with him) said: If I did not hear this from the Prophet (peace and blessings be upon him), may Allah make my ears deaf.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب القسامة / 16484