Musnad Ahmad 32:664

'Arim narrated to us, Mu'tamir narrated to us, he said: I heard my father narrating that Anas said: "It was said to the Prophet, may Allah bless him and grant him peace: 'If only you would go to 'Abdullah ibn Ubayy.' So the Prophet of Allah, may Allah bless him and grant him peace, set out to him and rode a donkey." The Muslims set out walking, and it was a salty, barren land. When the Prophet, may Allah bless him and grant him peace, went to him, he (Ibn Ubayy) said: "Get away from me, for by Allah, the smell of your donkey has offended me." A man from the Ansar said: "By Allah, the donkey of the Messenger of Allah, may Allah bless him and grant him peace, is better in smell than you." A man from his (Ibn Ubayy's) people became angry for 'Abdullah's sake. Then the companions of each of them became angry for their sake. He said: There was striking between them with palm branches, hands, and sandals. It reached us that it was revealed concerning them: {And if two factions among the believers should fight, then make settlement between the two} [Al-Hujurat: 9].