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: 6099
Zaid b. Arqam reported that Allah's Messenger (may peace be upon him) said: O Allah,, grant forgiveness to the Ansar, the offspring of the Ansar and the offspring of the offspring of the Ansar. This hadith has been narrated on the authority of Shulba with the same chain of transmitters.