The people used to ask Messenger of Allah ﷺ about good, but I used to ask him about evil for fear that it might overtake me. Once I said, "O Messenger of Allah ﷺ! We were in ignorance and in evil and Allah has bestowed upon us the present good; will there by any evil after this good?" He said, "Yes." I asked, "Will there be good after that evil?" He said, "Yes, but it would be tained with Dakhan (i.e. Little evil)." I asked, "What will its Dakhan be?" He said, "There will be some people who will lead (people) according to principles other than my tradition. You will see their actions and disapprove of them." I said, "Will there by any evil after that good?" He said, "Yes, there will be some people who will invite others to the doors of Hell, and whoever accepts their invitation to it will be thrown in it (by them)." I said, "O Messenger of Allah ﷺ! Describe those people to us." He said, "They will belong to us and speak our language" I asked, "What do you order me to do if such a thing should take place in my life?" He said, "Adhere to the group of Muslims and their Chief." I asked, "If there is neither a group (of Muslims) nor a chief (what shall I do)?" He said, "Keep away from all those different sects, even if you had to bite (i.e. eat) the root of a tree, till you meet Allah while you are still in that state." (Using translation from Bukhārī 3606)   

أَنَّهُ سَمِعَ حُذَيْفَةَ بْنَ الْيَمَانِ يَقُولُ كَانَ النَّاسُ يَسْأَلُونَ رَسُولَ اللهِ ﷺ عَنِ الْخَيْرِ وَكُنْتُ أَسْأَلُهُ عَنِ الشَّرِّ مَخَافَةَ أَنْ يُدْرِكَنِي فَقُلْتُ يَا رَسُولَ اللهِ إِنَّا كُنَّا فِي جَاهِلِيَّةٍ وَشَرٍّ فَجَاءَنَا اللهُ بِهَذَا الْخَيْرِ فَهَلْ بَعْدَ هَذَا الْخَيْرِ مِنْ شَرٍّ؟ قَالَ نَعَمْ قَالَ فَهَلْ بَعْدَ ذَلِكَ الشَّرِّ مِنْ خَيْرٍ؟ قَالَ نَعَمْ وَفِيهِ دَخَنٌ قُلْتُ وَمَا دَخَنُهُ؟ قَالَ قَوْمٌ يَهْدُونَ بِغَيْرِ هَدْيِي تَعْرِفُ مِنْهُمْ وَتُنْكِرُ قُلْتُ هَلْ بَعْدَ ذَلِكَ الْخَيْرِ مِنْ شَرٍّ؟ قَالَ نَعَمْ دُعَاةٌ عَلَى أَبْوَابِ جَهَنَّمَ مَنْ أَجَابَهُمْ إِلَيْهِا قَذَفُوهُ فِيهَا قُلْتُ يَا رَسُولَ اللهِ صِفْهُمْ لَنَا قَالَ هُمْ مِنْ جِلْدَتِنَا وَيَتَكَلَّمُونَ بِأَلْسِنَتِنَا قُلْتُ فَمَا تَأْمُرُنِي إِنْ أَدْرَكَنِي ذَلِكَ؟ قَالَ تَلْزَمُ جَمَاعَةَ الْمُسْلِمِينَ وَإِمَامَهُمْ قُلْتُ فَإِنْ لَمْ تَكُنْ جَمَاعَةٌ وَلَا إِمَامٌ؟ قَالَ فَاعْتَزِلْ تِلْكَ الْفِرَقَ كُلَّهَا وَلَوْ أَنْ تَعَضَّ بِأَصْلِ شَجَرَةٍ حَتَّى يُدْرِكَكَ الْمَوْتُ وَأَنْتَ كَذَلِكَ قَالَ أَبُو عَمَّارٍ فِي حَدِيثِهِ صِفْهُمْ لَنَا قَالَ هُمْ مِنْ كَذَا وَيَتَكَلَّمُونَ بِأَلْسِنَتِنَا لَفْظُ حَدِيثِ الْوَلِيدِ بْنِ مُسْلِمٍ  

One who defected from obedience (to the Amir) and separated from the main body of the Muslims - if he died in that state-would die the death of one belonging to the days of Jahiliyya (i.e. would not die as a Muslim). One who fights under the banner of a people who are blind (to the cause for which they are fighting, i.e. do not know whether their cause is just or otherwise), who gets flared up with family pride, calls (people) to fight for their family honour, and supports his kith and kin (i.e. fights not for the cause of Allah but for the sake of this family or tribe) - if he is killed (in this fight), he dies as one belonging to the days of Jahiliyya. Whoso attacks my Ummah (indiscriminately) killing the righteous and the wicked of them, sparing not (even) those staunch in faith and fulfilling not his promise made with those who have been given a pledge of security - he has nothing to do with me and I have nothing to do with him. (Using translation from Muslim 1848a)   

عَنِ النَّبِيِّ ﷺ أَنَّهُ قَالَ مَنْ خَرَجَ مِنَ الطَّاعَةِ وَفَارَقَ الْجَمَاعَةَ فَمَاتَ مَاتَ مِيتَةً جَاهِلِيَّةً وَمَنْ قَاتَلَ تَحْتَ رَايَةٍ عِمِّيَّةٍ يَغْضَبُ لِلْعَصَبِيَّةِ أَوْ يَدْعُو إِلَى عَصَبِيَّةٍ أَوْ يَنْصُرُ عَصَبِيَّةً فَقُتِلَ فَقِتْلَةٌ جَاهِلِيَّةٌ وَمَنْ خَرَجَ عَلَى أُمَّتِي يَضْرِبُ بَرَّهَا وَفَاجِرَهَا لَا يَتَحَاشَى مِنْ مُؤْمِنِهَا وَلَا يَفِي لِذِي عَهْدِهَا فَلَيْسَ مِنِّي وَلَسْتُ مِنْهُ  

[Machine] "I have not come to sit with you, but I have come to inform you of a hadith that I heard from the Messenger of Allah ﷺ . I heard him say, 'Whoever removes his hand from obedience (to the ruler), he will meet Allah on the Day of Judgment with no proof for him. And whoever dies without a pledge of allegiance on his neck, he dies the death of ignorance.'"  

إِنِّي لَمْ أَجِئْكَ لِأَجْلِسَ إِنَّمَا جِئْتُكَ لِأُحَدِّثَكَ بِحَدِيثٍ سَمِعْتُهُ مِنْ رَسُولِ اللهِ ﷺ سَمِعْتُهُ يَقُولُ مَنْ خَلَعَ يَدًا مِنْ طَاعَةٍ لَقِيَ اللهَ يَوْمَ الْقِيَامَةِ وَلَا حُجَّةَ لَهُ وَمَنْ مَاتَ وَلَيْسَ فِي عُنُقِهِ بَيْعَةٌ مَاتَ مِيتَةً جَاهِلِيَّةً  

[Machine] The Messenger of Allah ﷺ informed them, saying, "I command you with five things that Allah has commanded me with: the congregational prayer, listening, obeying, migration, and jihad in the cause of Allah. Whoever separates himself from the congregation by the span of a hand has removed the bond of Islam from his neck, unless he returns. And whoever calls to an ignorant way, then he is from the dwellers of Hell." A man said, "O Messenger of Allah, even if he observes fasts and performs prayers?" He said, "Yes, even if he observes fasts and performs prayers. So, invoke with the supplication of Allah that He has given you the name Muslim believers, worshippers of Allah."  

أَنَّ رَسُولَ اللهِ ﷺ حَدَّثَهُمْ قَالَ وَأَنَا آمُرُكُمْ بِخَمْسِ كَلِمَاتٍ أَمَرَنِي اللهُ ﷻ بِهِنَّ الْجَمَاعَةُ وَالسَّمْعُ وَالطَّاعَةُ وَالْهِجْرَةُ وَالْجِهَادُ فِي سَبِيلِ اللهِ فَمَن خَرَجَ مِنَ الْجَمَاعَةِ قِيدَ شِبْرٍ فَقَدْ خَلَعَ رِبْقَةَ الْإِسْلَامِ مِنْ رَأْسِهِ إِلَّا أَنْ يُرَاجِعَ وَمَنْ دَعَا دَعْوَةً جَاهِلِيَّةً فَإِنَّهُ مِنْ جُثَا جَهَنَّمَ قَالَ رَجُلٌ يَا رَسُولَ اللهِ وَإِنْ صَامَ وَصَلَّى؟ قَالَ نَعَمْ وَإِنْ صَامَ وَصَلَّى فَادْعُوا بِدَعْوَةِ اللهِ الَّذِي سَمَّاكُمْ بِهَا الْمُسْلِمِينَ الْمُؤْمِنِينَ عَبَّادَ اللهِ  

The Prophet ﷺ said: He who separates from the community within a span takes off the noose of Islam from his neck. (Using translation from Abū Dāʾūd 4758)   

قَالَ رَسُولُ اللهِ ﷺ مَنْ فَارَقَ الْجَمَاعَةَ شِبْرًا فَقَدْ خَلَعَ رِبْقَةَ الْإِسْلَامِ مِنْ عُنُقِهِ