Sahih Muslim Book 31, Hadith Number 6100.
Chapter : The merits of the Ansar (Allah be pleased with them).
Anas reported that Allah’s Messenger (may peace be upon him) sought forgiveness for the Ansar and he said: I think (he also sought forgiveness) for the children of the Ansar and the slaves and the freed men of the Ansar. I have no doubt about it.