Ibn Mas'ud (May Allah be pleased with him) reported:
The Messenger of Allah (ﷺ) said, "Reviling a Muslim is Fusuq (disobedience of Allah) and killing him is (tantamount to) disbelief." <b>[Al-Bukhari and Muslim]</b>.
وعن ابن مسعود رضي الله عنه قال: قال رسول الله صلى الله عليه وسلم :
سباب المسلم فسوق، وقتاله كفر
((متفق عليه)).