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: 6109
Abu Usaid Ansari reported that he heard Allah's Messenger (may peace be upon him) as saying: The worthiest of the Ansar or the worthiest of the settlements and the clans of Ansar; the rest of the hadith is the same, but there is no mention of the story of Sa'd b. 'Ubida (Allah be pleased with him).