Sahih Bukhari Volume 002, Book 023, Hadith Number 359.
Narated By Ibn 'Umar : When 'Abdullah bin Ubai (the chief of hypocrites) died, his son came to the Prophet and said, "O Allah's Apostle! Please give me your shirt to shroud him in it, offer his funeral prayer and ask for Allah's forgiveness for him." So Allah's Apostle (p.b.u.h) gave his shirt to him and said, "Inform me (When the funeral is ready) so that I may offer the funeral prayer." So, he informed him and when the Prophet intended to offer the funeral prayer, 'Umar took hold of his hand and said, "Has Allah not forbidden you to offer the funeral prayer for the hypocrites? The Prophet said, "I have been given the choice for Allah says: '(It does not avail) Whether you (O Muhammad) ask forgiveness for them (hypocrites), or do not ask for forgiveness for them. Even though you ask for their forgiveness seventy times, Allah will not forgive them. (9.80)" So the Prophet offered the funeral prayer and on that the revelation came: "And never (O Muhammad) pray (funeral prayer) for any of them (i.e. hypocrites) that dies." (9. 84)