Sahih Bukhari Volume 009, Book 088, Hadith Number 174.
Hadith Section/Book: Sahih Bukhari Sahih Bukhari Book 88. Afflictions and the End of the War
Narrated By Sahl bin Sa'd : I heard the Prophet saying, "I am your predecessor at the Lake-Fount (Kauthar), and whoever will come to it, will drink from it, and whoever will drink from it, will never become thirsty after that. There will come to me some people whom I know and they know me, and then a barrier will be set up between me and them." Abu Sa'id Al-Khudri added that the Prophet further said: "I will say those people are from me. It will be said, 'You do not know what changes and new things they did after you.' Then I will say, 'Far removed (from mercy), far removed (from mercy), those who changed (the religion) after me!"