Sahih Bukhari Volume 2, Book 23, Hadith Number 420.

Narated By Sulaiman Ash-Shaibani : I heard Ash-Sha’bi saying, “I was told by a man who had passed with the Prophet (p.b.u.h) by a grave that was separate from the other graves that he (the Prophet) led them in the prayer and they prayed behind him.” I said, “O Abu ‘Amr! Who narrated that to you?” He replied, “Ibn Abbas.”