Sahih Bukhari Volume 5, Book 58, Hadith Number 136.

Narated By Usaid bin Hudair : A man from the Ansar said, “O Allah’s Apostle! Will you appoint me as you have appointed so-and-so?” The Prophet said, “After me you will see others given preference to you; so be patient till you meet me at the Tank (i.e. Lake of Kauthar). (on the Day of Resurrection).”