“Narrated Abdullah Radiallahu anhu : The Prophet Sallallahu Alaihi Wasallam said,
Abusing a Muslim is Fusuq (evil doing) and killing him is Kufr (disbelief).
Abdullah Radiallahu anhu se rivayat hai ki Rasoollallahu Sallallahu Alaihi Wasallam ne farmaya musalman ko gaali dena Fisq (belong to Fasiq) hai aur Qatl karna kufr hai.
Sahih Bukhari, Vol 9, Book 88, No. 197”