It was said to Anas bin Malik (RA): You must have heard this that Allah's Messenger (ﷺ) said: There is no alliance (hilf) of brotherhood in Islam. Anas said: Allah's Messenger (ﷺ) established the bond of fraternity between the Quraish and the Ansar in his home.
Hadith Referenceصحيح مسلم / كتاب فضائل الصحابة / 2529
Jubair bin Mut'im reported Allah's Messenger (ﷺ) as saying: There is no alliance (hilf) in Islam but (the hilf) established in the pre-Islamic days (for good). Islam intensifies and strengthens it.
Hadith Referenceصحيح مسلم / كتاب فضائل الصحابة / 2530