Narrated Ash-Shaibani:
Ash Sha’bi said, “I was informed by a man who had seen the Prophet going to a grave that was separate from the other graves and he aligned the people in rows and said four Takbir.” I said, “O Abu ‘Amr! who narrated (that) to you”? He said, “Ibn Abbas. ”
Sahih Bukhari, Volume 2, Book 23, Number 405