From Sahih Muslim (Hadith 581):
Abu Huraira reported:Verily Allah's Messenger (ﷺ) said: My Cistern has its dimensions wider than the distance between Aila and Aden, and its water is whiter than ice and sweeter than the honey diluted with milk, and its cups are more numerous than the numbers of the stars. Verily I shall prevent the (faithless) people therefrom just as a man prevents the camels of the people from his fountain. They said: Messenger of Allah, will you recognise us on that day? He said: Yes, you will have distinctive marks which nobody among the peoples (except you) will have; you would come to me with blazing forehead and bright hands and feet on account of the traces of ablution
Reference: Muslim 581