Mishkat al-Masabih 30 Fine Qualities كتاب المناقب 3

وَعَنِ ابْنِ عُمَرَ أَنَّ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ قَالَ: «لَا يَزَالُ هَذَا الْأَمْرُ فِي قُرَيْشٍ مَا بَقِيَ مِنْهُمُ اثْنَان» . مُتَّفق عَلَيْهِ

Ibn `Umar reported the Prophet as saying, “This matter will continue in Quraish as long as two of them remain[*]. * Mirqat , 5:508, explains this as meaning that the Caliphate will remain the prerogative of Quraish as long as two human beings survive. (Bukhari and Muslim.)