Sahih Muslim
The Book Pertaining to the Merits of the Companions (Allah Be Pleased With Them) of the Holy Prophet (May Peace Be Upon Him) (Kitab Al-Fadail Al-Sahabah)
Book Number: 031 / Hadith Number: 5905
This hadith has been narrated on the authority of 'Ubaidullah with the same chain of transmitter but with the addition of the words:" He abandoned saying prayer over the hypocrites who had died."