The Prophet, said, "Abusing a Muslim is Fusuq (evil doing) and killing him is Kufr (disbelief).  

قَالَ النَّبِيُّ ﷺ سِبَابُ الْمُسْلِمِ فُسُوقٌ وَقِتَالُهُ كُفْرٌ  

I heard the Prophet ﷺ saying, "Do not revert to disbelief after me by striking (cutting) the necks of one another."  

أَنَّهُ سَمِعَ النَّبِيَّ ﷺ يَقُولُ لاَ تَرْجِعُوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ  

Messenger of Allah ﷺ addressed the people saying, "Don't you know what is the day today?" They replied, "Allah and His Apostle know better." We thought that he might give that day another name. The Prophet said, "Isn't it the day of An-Nahr?" We replied, "Yes. O Messenger of Allah ﷺ." He then said, "What town is this? Isn't it the forbidden (Sacred) Town (Mecca)?" We replied, "Yes, O Messenger of Allah ﷺ." He then said, "Your blood, your properties, your honors and your skins (i.e., bodies) are as sacred to one another like the sanctity of this day of yours in this month of yours in this town of yours. (Listen) Haven't I conveyed Allah's message to you?" We replied, "Yes" He said, "O Allah! Be witness (for it). So it is incumbent upon those who are present to convey it (this message of mine) to those who are absent because the informed one might comprehend what I have said better than the present audience who will convey it to him.)" The narrator added: In fact, it was like that. The Prophet ﷺ added, "Beware! Do not renegade as disbelievers after me by striking (cutting) the necks of one another."  

أَنَّ رَسُولَ اللَّهِ ﷺ خَطَبَ النَّاسَ فَقَالَ أَلاَ تَدْرُونَ أَىُّ يَوْمٍ هَذَا قَالُوا اللَّهُ وَرَسُولُهُ أَعْلَمُ قَالَ حَتَّى ظَنَنَّا أَنَّهُ سَيُسَمِّيهِ بِغَيْرِ اسْمِهِ فَقَالَ أَلَيْسَ بِيَوْمِ النَّحْرِ قُلْنَا بَلَى يَا رَسُولَ اللَّهِ قَالَ أَىُّ بَلَدٍ هَذَا أَلَيْسَتْ بِالْبَلْدَةِ قُلْنَا بَلَى يَا رَسُولَ اللَّهِ قَالَ فَإِنَّ دِمَاءَكُمْ وَأَمْوَالَكُمْ وَأَعْرَاضَكُمْ وَأَبْشَارَكُمْ عَلَيْكُمْ حَرَامٌ كَحُرْمَةِ يَوْمِكُمْ هَذَا فِي شَهْرِكُمْ هَذَا فِي بَلَدِكُمْ هَذَا أَلاَ هَلْ بَلَّغْتُ قُلْنَا نَعَمْ قَالَ اللَّهُمَّ اشْهَدْ فَلْيُبَلِّغِ الشَّاهِدُ الْغَائِبَ فَإِنَّهُ رُبَّ مُبَلِّغٍ يُبَلِّغُهُ مَنْ هُوَ أَوْعَى لَهُ فَكَانَ كَذَلِكَ قَالَ لاَ تَرْجِعُوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ فَلَمَّا كَانَ يَوْمَ حُرِّقَ ابْنُ الْحَضْرَمِيِّ حِينَ حَرَّقَهُ جَارِيَةُ بْنُ قُدَامَةَ قَالَ أَشْرِفُوا عَلَى أَبِي بَكْرَةَ فَقَالُوا هَذَا أَبُو بَكْرَةَ يَرَاكَ قَالَ عَبْدُ الرَّحْمَنِ فَحَدَّثَتْنِي أُمِّي عَنْ أَبِي بَكْرَةَ أَنَّهُ قَالَ لَوْ دَخَلُوا عَلَىَّ مَا بَهَشْتُ بِقَصَبَةٍ  

The Prophet ﷺ said, "Beware! Do not renegade as (disbelievers) after me by striking (cutting) the necks of one another."  

قَالَ النَّبِيُّ ﷺ لاَ تَرْتَدُّوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ  

The Prophet ﷺ said to me during Hajjat-al-Wadaʿ, "Let the people keep quiet and listen." Then he said (addressing the people), "Beware! Do not renegade as disbelievers after me by striking (cutting) the necks of one another."  

لِي رَسُولُ اللَّهِ ﷺ فِي حَجَّةِ الْوَدَاعِ اسْتَنْصِتِ النَّاسَ ثُمَّ قَالَ لاَ تَرْجِعُوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ