Imam Zuhri (may Allah have mercy on him) narrates that the Prophet (peace and blessings be upon him) also said: "Every treaty that Islam has made, its severity has only increased, and Islam does not advocate this." However, the Prophet (peace and blessings be upon him) established brotherhood between the Quraysh and the Ansar.
Hadith Referenceمسند احمد / مسند باقي العشرة المبشرين بالجنة / 1655M
Hadith Gradingحکم دارالسلام:مرسل وقد ورد معناه في احادیث صحیحة کما فی مسلم : 2530