The Prophet, said, "Abusing a Muslim is Fusuq (evil doing) and killing him is Kufr (disbelief).
Sahih al-Bukhari Book 92, Hadith 27
← Previous Hadith The Prophet (ﷺ) said, "If anyone of you passed through our mosque or through our market while carrying arrows, he should hold the iron heads," or said, "..... he should hold (their heads) firmly with his hand lest he should injure one of the Muslims with it."

Sahih al-Bukhari Book 92, Hadith 26 Next Hadith → I heard the Prophet (ﷺ) saying, "Do not revert to disbelief after me by striking (cutting) the necks of one another."

Sahih al-Bukhari Book 92, Hadith 28