Sahih Muslim Book 030, Hadith Number 5682.
Hadith Section/Book: Sahih Muslim Sahih Muslim Book 30. The Excellent Qualities Of The Holy Prophet (PBUH) And His Companions
Chapter : The cistern of our Apostle (may peace be upon him) and its characteristics.
Sahl (b. Sa'd) reported: I heard Allah's Apostle (may peace be upon him) as saying: I shall go to the Cistern before you and he who comes would drink and he who drinks would never feel thirsty, and there would come to me people whom I would know and who would know me. Then there would be intervention between me and them. Abu Hazim said that Nu'man b. Abu 'Ayyash heard it and I narrated to them this hadith, and said: Is it this that you heard Sahl saying? He said: Yes, and I bear witness to the fact that I heard it from Abu Sa'id Khudri also, but he made this addition that he (the Holy Prophet) would say: They are my followers, and it would be said to him: You do not know what they did after you and I will say to them: Woe to him who changes (his religion) after me.