Sayyiduna Abu Huraira (may Allah be pleased with him) narrated from the Messenger of Allah (peace and blessings be upon him), he (peace and blessings be upon him) said: "Abusing a Muslim is wickedness and killing him is disbelief."
Hadith Referenceمسند اسحاق بن راهويه / كتاب البر و الصلة / 789
Hadith Takhrij«مسند ابي يعلي ، رقم : 4258 . سلسلة ضعيفه ، رقم : 4816 .»