Musnad Abu Ya'la al-Mawsili 108:190

'Amr ibn Muhammad al-Naqid narrated to us, Sufyan narrated to us, from 'Amr, from Jabir, who said: A man from the Emigrants (Muhajirun) kicked a man from the Helpers (Ansar). The Ansari said: "O for the Ansar!" And the Muhajiri said: "O for the Emigrants!" When the Prophet, peace and blessings of Allah be upon him, heard that, he said: "What is this call of the pre-Islamic era (Jahiliyyah)?" They said: "O Messenger of Allah, a man from the Emigrants kicked a man from the Helpers." He said: "Leave it, for it is foul." 'Abdullah ibn Ubayy ibn Salul said: "Have they really done it? If we return to Medina, the more honorable will surely drive out the meaner from it." 'Umar said: "Let me, O Messenger of Allah, strike the neck of this hypocrite." He said: "Leave him, lest people say that Muhammad kills his companions."