Sunan an-Nasa'i 150

أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكٍ، عَنِ الْعَلاَءِ بْنِ عَبْدِ الرَّحْمَنِ، عَنْ أَبِيهِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم خَرَجَ إِلَى الْمَقْبُرَةِ فَقَالَ ‏"‏ السَّلاَمُ عَلَيْكُمْ دَارَ قَوْمٍ مُؤْمِنِينَ وَإِنَّا إِنْ شَاءَ اللَّهُ بِكُمْ لاَحِقُونَ وَدِدْتُ أَنِّي قَدْ رَأَيْتُ إِخْوَانَنَا ‏"‏ ‏.‏ قَالُوا يَا رَسُولَ اللَّهِ أَلَسْنَا إِخْوَانَكَ قَالَ ‏"‏ بَلْ أَنْتُمْ أَصْحَابِي وَإِخْوَانِي الَّذِينَ لَمْ يَأْتُوا بَعْدُ وَأَنَا فَرَطُهُمْ عَلَى الْحَوْضِ ‏"‏ ‏.‏ قَالُوا يَا رَسُولَ اللَّهِ كَيْفَ تَعْرِفُ مَنْ يَأْتِي بَعْدَكَ مِنْ أُمَّتِكَ قَالَ ‏"‏ أَرَأَيْتَ لَوْ كَانَ لِرَجُلٍ خَيْلٌ غُرٌّ مُحَجَّلَةٌ فِي خَيْلٍ بُهْمٍ دُهْمٍ أَلاَ يَعْرِفُ خَيْلَهُ ‏"‏ ‏.‏ قَالُوا بَلَى ‏.‏ قَالَ ‏"‏ فَإِنَّهُمْ يَأْتُونَ يَوْمَ الْقِيَامَةِ غُرًّا مُحَجَّلِينَ مِنَ الْوُضُوءِ وَأَنَا فَرَطُهُمْ عَلَى الْحَوْضِ ‏"‏ ‏.‏

It was narrated from Abu Hurairah that the Messenger of Allah (ﷺ) went out to the graveyeard and said:"Peace be upon you, abode of believing people. If Allah wills, we shall join you soon. Would that I had seen our brothers." They said: "O Messenger of Allah, are we not your brother?" He said: "You are my Companions. My brothers are those who have not come yet. And I will reach the Hawd before you." They said: "O Messenger of Allah, how will you know those of your Ummah who come after you?" He said: "Don't you think that if a man has a horse with a white blaze and white feet among horses that are solid black, he will recognize his horse?" They said: "Of course." He said: "They will come on the Day of Resurrection with glittering white faces and glittering white hands and feet because of Wudu', and I will reach the Hawd before them

Reference

Sunan an-Nasa'i 150

In-book

Book 1, Hadith 151