Sahih Muslim Book 31, Hadith Number 6144.

Chapter : Fraternity established by Allah’s Apostle (may peace be upon him) amongst the companions (Allah be pleased with them).

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.