Sahih Bukhari Volume 002, Book 023, Hadith Number 424.
Narated By Ibn Abbas : The Prophet (p.b.u.h) offered the funeral prayer of a man one night after he was buried, he and his companions stood up (for the Prayer). He had asked them about him before standing, saying, "Who is this?" They said, "He is so and so and was buried last night." So all of them offered the funeral prayer.