Imam al-Shafi'i (may Allah have mercy on him) said: Likewise, if one man among them breaks the treaty and fights, the Imam may fight their whole group. Three men of Quraysh helped against Khuza'ah, while Khuza'ah were in the treaty of the Prophet (peace and blessings be upon him), and they took part in fighting them. So the Prophet (peace and blessings be upon him) marched against Quraysh in the year of the Conquest because of the treachery of those three men, and because the rest did not help Khuza'ah and gave shelter to those who had fought Khuza'ah.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18858