Authentic
Sunan Ibn Majah 3944
“I shall reach the Cistern (Haud) before you, and I will boast of your great numbers before the nations, so do not fight one another after I am gone.’”
" أَلاَ إِنِّي فَرَطُكُمْ عَلَى الْحَوْضِ وَإِنِّي مُكَاثِرٌ بِكُمُ الأُمَمَ فَلاَ تَقْتَتِلُنَّ بَعْدِي "