Isma'il bin Ibrahim bin Uqbah narrates from his paternal uncle Musa bin Uqbah that Banu Nufathah, who are of Banu al-Dil, attacked Banu Ka'b while they were within the period of the treaty that was between the Messenger of Allah (peace and blessings be upon him) and Quraysh. Banu Ka'b were in the peace with the Messenger of Allah (peace and blessings be upon him), while Banu Nufathah were with Quraysh. Banu Bakr helped Banu Nufathah, and Quraysh supported them with weapons and slaves, but Banu Mudlij kept apart and fulfilled the covenant. The narrator says: Safwan bin Umayyah (may Allah be pleased with him), Shaybah bin Uthman (may Allah be pleased with him) and Suhayl bin Amr (may Allah be pleased with him) helped them. Then Banu al-Dil attacked Banu Amr and their common people, shed the blood of women, children and weak men, and some of them entered the house of Budayl bin Warqa' (may Allah be pleased with him). The narrator says: A rider from Banu Ka'b came and told the Messenger of Allah (peace and blessings be upon him) of their condition, and of the help Quraysh had given against them. Then he mentioned the preparations of the Prophet (peace and blessings be upon him) and Abu Bakr (may Allah be pleased with him) coming in to him. The narrator says that Abu Bakr (may Allah be pleased with him) said: O Messenger of Allah (peace and blessings be upon him), do you intend to set out? He (peace and blessings be upon him) said: "Yes, I intend to fight." Abu Bakr (may Allah be pleased with him) said: Perhaps you intend the Romans. He (peace and blessings be upon him) said: "No." Abu Bakr (may Allah be pleased with him) asked: Do you intend to fight the people of Najd? He (peace and blessings be upon him) said: "I have no intention of fighting them." He asked: Do you intend to fight Quraysh? He (peace and blessings be upon him) said: "Yes." Abu Bakr (may Allah be pleased with him) said: Is there not a treaty between you and them? He (peace and blessings be upon him) said: "Have you not heard what they did to Banu Ka'b?" And the Messenger of Allah (peace and blessings be upon him) announced jihad among the people.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجزية / 18860