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-Fada'il Al-Sahabah)
Muslim :: Book 31 : Hadith 6158
This hadith has been narrated on the authority of 'Imran b. Husain through another chain of transmitters (and the words are): The best generation of this Umma is the generation to which I have been sent, then the next one, and there is an addition in the hadith transmitted on the authority of Abu 'Awana (and the words are): And Allah knows best whether he made a mention of the third (generation) or not; the rest of the hadith is the same as transmitted by Zahdam on the authority of 'Imran. And in the hadith transmitted by Hisham on the authority of Qatada there is an addition of these words: They take an oath whereas they are not asked to take.