Narrated Ibn `Umar:

When `Abdullah bin Ubai (the chief of hypocrites) died, his son came to the Prophet (s.a.w.a.) and said, "O Allah's Messenger (s.a.w.a.)! 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 Messenger (s.a.w.a.) 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 (s.a.w.a.) 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 (s.a.w.a.) 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)

Narrated `Umar bin Al-Khattab:

When `Abdullah bin Ubai bin Salul died, Allah's Messenger (s.a.w.a.) was called upon to offer his funeral prayer. When Allah's Messenger (s.a.w.a.) stood up to offer the prayer, I got up quickly and said, "O Allah's Apostle! Are you going to pray for Ibn Ubai and he said so and so on such and such occasions?" And started mentioning all that he had said. Allah's Messenger (s.a.w.a.) smiled and said, "O `Umar! Go away from me." When I talked too much he said, "I have been given the choice and so I have chosen (to offer the prayer). Had I known that he would be forgiven by asking for Allah's forgiveness for more than seventy times, surely I would have done so." (`Umar added): Allah's Messenger (s.a.w.a.) offered his funeral prayer and returned and after a short while the two verses of Surat Bara' were revealed: i.e. "And never (O Muhammad) pray for any of them who dies . . . (to the end of the verse) rebellion (9.84)" -- (`Umar added), "Later I astonished at my daring before Allah's Messenger (s.a.w.a.) on that day. And Allah and His Apostle know better."