The Prophet ﷺ said to me during Hajjat-al-Widaʿ: Let the people keep quiet and listen. Then he said (addressing the people), "Do not (become infidels) revert to disbelief after me by striking the necks (cutting the throats) of one another (killing each other).  

أَنَّ النَّبِيَّ ﷺ قَالَ لَهُ فِي حَجَّةِ الْوَدَاعِ اسْتَنْصِتِ النَّاسَ فَقَالَ: «لاَ تَرْجِعُوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ۔»  

The Prophet ﷺ said, "Wailakum" (woe to you) or "waihakum" (May Allah be merciful to you)." Shuʿba is not sure as to which was the right word. "Do not become disbelievers after me by cutting the necks of one another."  

عَنِ النَّبِيِّ ﷺ قَالَ: «وَيْلَكُمْ» أَوْ «وَيْحَكُمْ» قَالَ شُعْبَةُ: شَكَّ هُوَ «لاَ تَرْجِعُوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ۔»

وَقَالَ النَّضْرُ عَنْ شُعْبَةَ: «وَيْحَكُمْ» وَقَالَ عُمَرُ بْنُ مُحَمَّدٍ عَنْ أَبِيهِ: «وَيْلَكُمْ» أَوْ «وَيْحَكُمْ»