Sahih al-Bukhari 7050

Abu Hazim reported that he heard Sahl ibn Sa'd say that he heard the Prophet, may Allah bless him and grant him peace, say, "I will be your forerunner to the Basin. Whoever comes to it will drink from it. Whoever drinks from it will never be thirsty again. Some people will come to me whom I will recognise and they will recognise me but then a barrier will be put up between me and them." Abu Hazim said, "An-Nu'man ibn Abi 'Ayyash heard me when I was reporting this. He asked, 'Is that how you heard it from Sahl?' 'Yes,' I replied. He said, 'I was present with Abu Sa'id al-Khudri and I heard him add to it, "They are from me." It will be said, 'You do not know what they changed after you.' I will say, 'Far away! Far away with those who changed after me!'"'"