The Book of Faith
1/29. Chapter:
Clarifying the meaning of the Statement of the Prophet (saws): "Do not revert to disbelief (Kuffar) after I am Gone, striking one another's necks"
Sahih Muslim
وَحَدَّثَنِي أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، وَأَبُو بَكْرِ بْنُ خَلاَّدٍ الْبَاهِلِيُّ قَالاَ حَدَّثَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، حَدَّثَنَا شُعْبَةُ، عَنْ وَاقِدِ بْنِ مُحَمَّدِ بْنِ زَيْدٍ، أَنَّهُ سَمِعَ أَبَاهُ، يُحَدِّثُ عَنْ عَبْدِ اللَّهِ بْنِ عُمَرَ، عَنِ النَّبِيِّ صلى الله عليه وسلم أَنَّهُ قَالَ فِي حَجَّةِ الْوَدَاعِ " وَيْحَكُمْ - أَوْ قَالَ وَيْلَكُمْ - لاَ تَرْجِعُوا بَعْدِي كُفَّارًا يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ " .
It is narrated on the authority of Abdullah b. Umar that the Apostle (may peace and blessings be upon him) observed on the occasion of the Farewell Pilgrimage Woe unto you distress unto you! Don't turn back as unbelievers after me by striking the necks of one another.
Reference : Sahih Muslim 66bIn-book reference : Book 1, Hadith 131USC-MSA web (English) reference : Book 1, Hadith 126