Sayyiduna Abdullah bin Busr al-Mazini (may Allah be pleased with him) narrates from the Messenger of Allah (peace and blessings be upon him) that he (peace and blessings be upon him) said: "On the Day of Resurrection there will be no one whom I do not recognize." It was said: "O Messenger of Allah (peace and blessings be upon him), how will you recognize them amid such a multitude of creatures?" He (peace and blessings be upon him) said: "Tell me, if you entered an enclosure in which there were horses of pure black colour, and among them was a horse whose forehead and legs were a shining white, would you not recognize it among them all?" He said: "Of course (I would surely recognize it)." He (peace and blessings be upon him) said: "Then indeed, on that day my Ummah will be ghurrun muhajjalun, that is, with shining faces and shining hands and feet, from the traces of ablution (wudu)."
Hadith Referenceالمعجم الأوسط / باب الألف / 4
Hadith Takhrij«أخرجه الضياء المقدسي فى «الأحاديث المختارة» برقم: 93، 95، 96، والترمذي فى «جامعه» برقم: 607، وأحمد فى «مسنده» برقم: 17969، والبزار فى «مسنده» برقم: 3500»