Sunan An-Nasai, Chapter: The Book of Purification

that the Messenger of Allah (saw) went out to the graveyard 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 brothers?" 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." (Sahih)