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: 6144
It was said to Anas b. Malik: You must have heard this that Allah's Messenger (may peace be upon him) said: There is no alliance (hilf) of brotherhood in Islam. Anas said: Allah's Messenger (may peace be upon him) established the bond of fraternity between the Quraish and the Ansar in his home.