Sahih al-Bukhari 7077
Book 92: Afflictions and the End of the World · Narrated by Ibn `Umar
Arabic
حَدَّثَنَا حَجَّاجُ بْنُ مِنْهَالٍ، حَدَّثَنَا شُعْبَةُ، أَخْبَرَنِي وَاقِدٌ، عَنْ أَبِيهِ، عَنِ ابْنِ عُمَرَ، أَنَّهُ سَمِعَ النَّبِيَّ صلى الله عليه وسلم يَقُولُ " لاَ تَرْجِعُوا بَعْدِي كُفَّارًا، يَضْرِبُ بَعْضُكُمْ رِقَابَ بَعْضٍ ".
English translation
Narrated Ibn `Umar:I heard the Prophet (ﷺ) saying, "Do not revert to disbelief after me by striking (cutting) the necks of one another
Reference: Sahih al-Bukhari 7077, Book of Afflictions and the End of the World. English translation by Dr. Muhammad Muhsin Khan.