Sahih al-Bukhari, Volume 4, Book 56, Hadith 805 (USC-MSA) ⓘ
Narrated Abu Huraira: Allah's Messenger said, "The Day of (Judgment) will not be established till there is a war between two groups whose claims (or religion) will be the same."
حَدَّثَنَا الْحَكَمُ بْنُ نَافِعٍ، حَدَّثَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، قَالَ أَخْبَرَنِي أَبُو سَلَمَةَ، أَنَّ أَبَا هُرَيْرَةَ ـ رضى الله عنه ـ قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم " لاَ تَقُومُ السَّاعَةُ حَتَّى يَقْتَتِلَ فِئَتَانِ دَعْوَاهُمَا وَاحِدَةٌ " .
also referenced under: Book 61, Hadith 115 (In-Book) & Hadith 3608 (DarusSalam)