It is narrated from a Companion (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: Soon there will be a people among the dhimmis; whoever kills any one of them will not even smell the fragrance of Paradise, although the fragrance of Paradise can be perceived from a distance of seventy years.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16590